Well,
Sound is the first to go on bootlegs. I am not sure if it is because the sound chips are on the top board and more sustable to natural and UV light (thus erasing them) or if sound data is just more picky about the chip it is coming out of... or whatever... but the bootlegs I have had in the past, all but one had problems with sound and nothing else. By the way, the real SDB carts are going down in price now. I have seen some real ones for $150 being offered at various places. Your best bet is to try european shops/sellers. As a rule, there are much less bootleg games over there. I bought a pop n bounce, super dodgeball, and a Neo Turf Masters (all highly bootleged games) from European places... and they all seemed offended that I asked if they were original or not... and of course they were all original (and basicly mint to boot).
-Nick