one thing i noticed between the two, is the timing on your pop is different between thunder and indy. not better or worse but each truck will suit different people differently. its not just a height thing but also relates to the position of the kingpin and hangars, as well as the angles and geometry. as for the turn its pretty easy to switch between the two but as a general rule, i'd say if you like yr indys loose go with ace, if you ride them med or tighter go with thunder. thunders have a real responsive, snappy quick turn but its not very deep. thunders are also lighter if you care about that...
in saying all that, contrary to what some people like to think, thunders can be ridden loose and work well on round wall also once you dial them in.
personally, if i was skating mostly technical street shit or back and fore half pipe, i'd def go with thunders.
round wall transition or slappy style loose carving street shit = ace. i'm old and love small tight fucked up trannies, carve grinds and slappies, so mostly skate ace these days.