Biological, and here's a tip if you like cheating. When you are in the second area go on a training battle and loads of switching scenes will appear, when all of them go past (they go all the time) click on the blue ring and then you will be lvl 30 with unlimited cash.
Im Psychological to see what it is like... i heard it not so good so challenges are a good thing... i needed that lv 30 and unlimited cash cash one though...
currently hydraulic on challenging mode , going to be psycho on heroic.i really enjoy hydro , and his talent builds , mostly instinct based with lots of debuffs.
biological,for the reason that it is made for heavy physical attacks,and less about status ailments which I don't really pay attention to.I think I made a fairly good character with it as well.I played against a character that was lvl 30 hydraulic,and found that the abilities for biological are a bit better for me.