tha game guru will answer your question, i have played armor core 2 and its a great game, i love mech games, and if your into those type of games them, it might just be worth renting but not buying, there is to much slowdown, and i mean slow slow down, i would definatly recommend Z.O.E. because it is a mech game like armoor core 2 but much better, and t evemn coems with mgs2 demo, but if your just gonn aget it for the demo, then your smokin crack
shadow of destiny, has been getting some great ratings and desreve a look at before passing up this game.
bottom line:
if you want a straight on fighter with no apparent story line then get Armor Core 2,
if you want a great Mech title with a beautiful story and action, get z.o.e.
and if you are into adventure game, puzzles and that sort of stuff, look into Shadow of Destiny.