NiCd or Li-Ion is really about the battery pack rather than the tool. Or it would nearly be if manufacturers offered the choice of both battery options for single product models.

Al these NiCd cordless packs, including DeWalt's, just use various cylindrical cells wired in series. There are even instructions on the net of how to replace the cells in your own packs, which can be a lot cheaper than buying a new pack.

I wouldn't go out of my way to buy a large supply of battery packs or products unless they'd see immediate use. If you don't need them now, don't buy them, because newer stuff will always be coming out at prices that will be more attractive.

Everything on this subject that I've posted above is 100% empirical. Strictly based on personal experience, so there may be others out there with different findings.