I like both but as i said only prefer one over the other depending on the quality of the last movie that they in, the recent one was predators which was a decent sequel especially compared to the crossovers. I like the xenomorphs from aliens the best out of all depictions, and the first predator creature from the first film.
Both are scii/fi horrors but in the alien franchise, namely the first two perhaps three, it had a more tense atmosphere, kept you on the edge of your seat. Predator while brutal and gory had a slightly tense and suspenseful atmosphere but was action orientated and amusing.
