To the death:
http://forum.arcadecontrols.com/index.php?topic=61944.0I have both: P360 and U360.
P360 I use for shmups games only. BUT -> I have moded shaft (shorter SlikStik heavy shaft with heavy ball, better mod is with lighter spring and lighter shaft and ball) and actuator (I must only touch joystick to engage).
Why U360 not for shmups? Because default spring and 2 additional old springs are wrong. Now I will test new spring (maybe in weekend), maybe will be fine.
U360 is great without modify, P360 is weak without modify.
In U360 you can easy enable different modes, in P360 it's very hard, I can say impossible, generally it's 8-way stick only.
Summary:
- P360 without mod -> throw to trash
- U360 without mod -> excellent for all but shmups
- P360 with mod -> excellent for shmups
- U360 with new spring -> ... we will see

If you don't want to buy both joysticks (probably you don't want

) then buy U360.
And remember - sometimes (for some games) standard joystick with microswitches will be better than P360 or U360 then you always can mount one of this type joystick to your cabinet.