I just did a little fumbling about on the net for testosterone isocaproate. If you compare the molecular weight of the enanthate ester, 134, to isocarproate ester, 116, it's fairly close. But if you look at Propionate, 74, it's much shorter then iso. So I suspect that isocarproate will be more like enanthate then like propionate.
So I don't really see a big reason to use it other then it's available and others are not. And that's a BIG reason. Some is always better then none.