My god.. Search for it, but heres the lowdown;
ISIS Cranks = Stiffer feel, last longer (wont round off).
ISIS BBs = Lower price isis bbs wont last as long as a same priced sq bb, therefore can be costly.
SQ Cranks = Slightly less stiffer feel than isis, will round off if not kept tight.
SQ BBs = Cheap to replace, last quite a long time.
Thats it really :o
Oh yeah, if your riding stock; 170mm length is best (Y)
Hope iv helped, Sam