As stated above, it will depend on your amp and system. KT150s definitely sound better in my Zesto Bia Select 200.
With that said, I've found KT150s to be unreliable. I've had to replace two in less than 250 hours.
kt88 vs kt150
my amp (Rogers EHF200 Mk 2) will take KT-88, KT-120 and KT-150. I have only tried it with the 150's. I'd be interested in comments on the sonic differences to expect with KT-88's. I understand that the bass is likely better with the 150's, but it seems a little boomy with my system.