It should be noted that if you look at Baseball Prospectus, they use a slightly different version of the Isolated Power stat. It operates on the assumption that speed, rather than power, is the cause of most triples. To save a trip, I'll quote the entire stat glossary entry. I don't think one method is better than the other. If you want to eliminate the speed factor, use the BP method. If you're simply looking at extra base hits, use the standard formula. Of course, if you want to calculate quickly and easily, use the standard formula. If you're into whipping up spreadsheets, what the heck, put both formulas in. The most important thing to remember is if you're looking at Baseball Prospectus' site, you're going to see a different number than you'll see elsewhere.