I have all 3, and use them all ... they all have advantages and disadvantages.
Absolutely LOVE my Craftsman 19.2V drill / impact driver set
You can get all sorts of other C3 tools as well. I have the hedge-trimmer and a couple of different lights. Despite having any written confirmation anywhere that I could find, you can also use the 19.2V lithium-ion batteries interchangably with the Ni-Cad ones. The intelligent charger that comes with the Li-Ion set can be used to charge both types of batteries.
Wait for Sears to have a tool sale.
I paid about $150.00 CDN for both drivers, 1 Li-Ion battery, and a charger. I ordered the flashlights at the same time because they were offering a 20% discount if you ordered 3 or more items. It worked out that I got the flashlights for free!