You'd think that with something like a bongo that chip tunes would be better, as long as bongos can be somewhat aproximated. The low grade samples used on PCE (especialy with HuCARDs) are going to be really aliased and scratchy but the chip makes really smooth tones.
Super Star Solider has some synth cool tom sounds that I'm pretty sure are PSG because it seems like they wouldn't sound that great as samples (plus, they'd eat more memory). Of course, I'm not skillful enough with an emulator or other debugging stuff to actually verify this one way or another.
Regarding the SNES, there are a lot of samples used with it. That's kind of the way it was designed. However, it has so many ways of manipulating samples in real time that it can do a lot more than just playing files in a sequence. Samples are very...plastic...on the SNES, very flexible. You can use a sample that is something pretty low fi but sort of rescue it with pitch adjustments, reverb, delay, etc. Sadly this is hugely overdone but when handled correctly can be amazing. Games like Mother 2 and Yoshi's Island have incredible soundtracks.
However, it's also possible to synthesize drums on the SNES, which people are going to want to do for many reasons.
