There are advantages to each, depending on what you are looking for. NiCD batteries have almost twice the charge/discharge cycle life (NiCD is about 500+ cycles, NiMH and Li-Ion are about 300+), lower self discharge rate (NiCd is ~20%/month@77F, NiMH is ~30%/month@77F, Li-Ion is only 3%/month@77F), and NiCD has a wider operating temperature range (NiCD is -22 to 140F, NiMH is -4 to 122F - although they pretty much are useless below 14F, Li-Ion is +14 to 122F). NiCD batteries have more of a memory effect (NiMH have a little and Li-Ion has none), but can be compensated for by periodic conditioning. NiCD is less sensitive to heat, NiMH is fairly sensitive, and Li-Ion is extremely sensitive to heat, particularly for charging. NiMH and Li-Ion batteries have greater storage density so can continue working longer per charge than NiCD, but at the cost of a reduced life span. NiCd batteries must be properly recycled, NiMH are recommend but not required, and Li-Ion can be thrown away without restriction. NiCD batteries are much cheaper than either of the other two. Both NiCD and NiMH are shipped uncharged and must be charged before initial use, and NiMH also need to be further conditioned before initial use (or after storage for 3 months or longer) or their capacity will be greatly reduced.
I've stuck with NiCD batteries, simply because I can get battery packs for my Makita for less than $20 a piece (and they are twice the capacity of the originals). A pack will last me about 5 years or so before needing to be replaced. They may not last as long per charge as the others, but at that price, it's pretty easy to have extras on hand to compensate for that, and they have a longer service life.
YMMV.
Cheers,
Brad