RE: I sonic 145 VS F-Type 138
no tuning == carve (but your brother doesn't think its fast (gps? (have since a few days a C133T but am still waiting for a decent test day, but man that board is fully balanced == 0 tecnique necessary)))
HTS Superfast might be what he is looking for (should they still be in business), true plug an play like the carve but lighter. Sorry about your other choices, just don't know those boards.
iS is designed for a very narrow application like all other full blood slamon boards. Built for high performance over a very short period (iS, Manta whatever, I think they all would fail the coin test (sooner or later, wood a bit sooner))