I can forgive him being wishy-washy up until the end; after everything he's seen to that point, he still ends up believing Church one last time? Church is right; he is a fatuous ra-ra boy (but that's probably how he got his rank.)
I think the novel improved on a few places in character development and world building. Probably the biggest improvement is while it loses Plunket's art, it also loses all of the laughably over the top gore (the Alien pitching that skull at the dropship remains the most ludicrous thing in an otherwise serious comic I've seen.)