Predators are overpowered in this game and that's a fact (Well, for X360 and PS3 it is). It doesn't matter if you're an epic Alien against a decent Predator and he kills you 1 time to your every 10. That's a difference in skill and/or connection, and not a difference in character potential. It doesn't matter what your own personal experiences are, it needs to be calculated through numbers, statistics and abilities. 'The best', or in this case, 'most powerful' is calculated by four things. These are Connection, Skill, Species and Map. Though I say personal experience doesn't matter, unless you have access to the hard numbers and statistics, it is the only way to discover them, so I will draw on my own specific experience to demonstrate my point.
Many players regard ch281 AKA CHAKRAMMblade (Or however you spell it) as the best Alien on the PS3 servers, myself included, with the exception of one other named Hameln_liebe_M whom I consider to be a good contender for that title. I, and many others, consider myself to be a fantastic Predator (Though I am far from the best). I played Ch281 1on1 on 3 maps, my host (He challenged me), Predator vs Alien and I doubled his score with no weapons, no glitched heavy spam (like so many "good" players love to use), no fake heavies (despite him using them), and was barely trying. I allowed him to get up from knock-down several times. We played on several maps and it was the same every time, and I was getting really bored. I had no idea who he was at this point, and, getting fed up with him keep readying up as an Alien after hoping he would switch to Pred after the first match, I decided to switch it to Jungle and went to Alien, intending to fight AvA but he switched to Predator just as I hit go. Now, bear in mind that I am host, though his connection is so good that the advantage I had was minimal. He then proceeded to heavy spam me constantly, barely ever needing the light attack unless I managed to get the drop on him and start a heavy which nearly never happened. I could do nothing and truthfully was a little annoyed that he wasn't showing me the same fair courtesy I showed him. I gave up after he was 12-0 up because no matter what I did, I could barely hit him, much less kill him. I sent him a message and said that I was bored and this was pointless unless he was prepared to go Pred. We chatted and then he sent me a message asking to host. We then played 5 or 6 games on his connection, all on Refinery, me as Pred and him as Alien and he did manage to beat me in 2 of them due to stealth and the host advantage lying with him, though it was close and truthfully I was still bored and not trying as hard as I could have been, such as rushing round corners when I'm leading, knowing he was there waiting to ambush me with his OMG GODLY connection that I couldn't counter in time. I let him get back up often too.
CH281 is a nice guy and a godly Alien but the truth is even the BEST Alien in the whole world can not compete with a Predator 1v1 if both are used to the full potential, unless there is a significant connection advantage or the match takes place in the Pyramid, and the latter is not that much of an advantage if the Predator can score the lead and force the Alien to come to him. In the fairest fight I could possible manage with ch281, I was still dominating and one thing is for sure, it was NOT because I was the better player. When we went AvA, 4 matches, 2 hosts a piece I only won one and that was on my host and very, very close. On his hosts he dominated me by alot. Connection > Skill sure, and he had the superior one so he had the advantage, sure, but even if we had even connections (impossible to achieve, but IF) I still would not like my chances against him AvA and would bet my savings on him winning. We did not battle Pred v Pred.
Now, to finally finish my point, if a Pred was used to it's full potential and he was too smart to allow himself to get in to a position where he could be tailed from a wall, all a Pred has to do to kill an Alien everytime without fail is press L1, L1, L1, L1, L1, L1, L1 (in that order :p) as fast as he can and he is guaranteed a kill because even if the first one gets countered with a light, he will be invulnerable to counter a second time due to the glitch. What's more if the Alien goes for the heavy while the Predator is stunned you'd think that the Pred would have to light attack the Alien or it will connect its heavy before the Pred connects his glitched heavy. Well, unless you are suffering from pretty bad lag, you're wrong. That Pred's glitch heavy will be faster than the Alien's heavy every time leaving the Alien with ultimately one option: hit and run. He can't heavy because the Pred's is faster.. He can't light because it won't have any effect other than a trade of a meager quarter-bar of damage for a health-halving strike with stun effects. All he can do is counter and jump away to avoid that glitch heavy. This is before you even start to incorporate the weapons. With the Disk and a keen understanding of the geography of each map, the Predator can know where any player is at any time with the locator function of the Disk. It works at huge distance too. Give me that over seeing through walls any day of the week. The ability to track enemies over vast distances is probably the most useful function of any of the weapons in my opinion. The Mines which net so many players a lot of kills just because they know where to strategically press R2 to lay one. Need I say anything about the caster? The Spear is probably the only weapon that isn't overpowered due to how difficult it is to hit good players that know to stay on the move, and how difficult it is to hit.. well.. anything when you're not the host due to slower ejection and traveling speeds.
Now, 1v1 is very different to an actual group MSTDM or DM and I acknowledge that. Different strengths for the Alien come in to play, and the dynamics and flow of the game work very differently for all species. The Alien has many strengths the Predators do not but the Predators strengths are far more numerous and easier to apply, and ultimately, land more kills with.
Really the only thing the Alien has going for it is the wall-tailing ability which takes quite a bit of skill to use effectively if you aren't in the Pyramid, its ability to escape so quickly on to walls and live to fight another day, and the hiss because it's so damned cute.
Also, I could make a huge case and point for why the Marine is stronger than the Alien too, but instead I'll just say this: The gap is a lot smaller than the AVP comparison, and gets even smaller at higher levels of play, but the Marine controls the melee triangle over an Alien unless the Alien fake heavies him (which personally I never do to any species unless its PredVPred and the guy is good, as I find it unfair). Even the fake-heavy can be predicted and dealt with if you have enough experience and intuition for your opponent's actions. That's short-range advantage AND long-range advantage (due to the non-existence of the Alien's long-range capabilities).
For my personal opinion, I think it's all about how you look at it. I think the problem is not that the Predator is overpowered, but the Alien is underpowered. When developers make a game they have to cater to 2 types of fans: 1. Those that want realism. 2. Those that want a fair, fun, balanced game. Most of the time, these two things contradict one-another and so they try to find a balance between the two as they can't have both. Making the Alien more powerful would have been a positive step towards both realism and balance. With the PC version they made the Predator a lot weaker, that's a step towards balancing but away from realism. Marines should not be able to knock either an Alien or a Predator down. I think that is neither realistic nor a balanced form of play when Marines can take down 2-3 Aliens with just a Shotgun and his Kung-Fu (And yes it is possible, I have done it many times).
My advice: Take the game for what it is, free of expectation of what you think it should be, or how other players should play (Yes I'm looking at you people who bitch about others using the caster) and enjoy it for what it is. It is a GOOD game and though it has its flaws, there's very few games like it and it is a beautiful work of art in its own right. It's not perfect, but nothing is. Strive for excellence, not perfection.