The snap-on is a good tool, but how good in practical terms for the backyard mechanic? Last I checked, I don't hard-connect one to another and let them fight to the death for which one will break first.
I posted the same question a year or so ago. The recommendation varied, but many cited the snap-on video of it "smoking" its IR competition. This only tells me one thing - that IR IS its biggest competitor, and thus likely one of the best.
I shopped the snap-on and the top of the like 1/2" drive IR cordless (360W, I think). I ended up with more batteries, a flashlight, charger, bag and the wrench for a fair amount less than I could get the snap-on for.
Score one for the IR - cheaper.
The Snap-on does not use a Li-ion battery. I prefer them, since as a backyard mechanic, I neither keep my batteries constantly charging, or constantly cycling due to use. Li-ion batteries, like on the IR, have far lower self discharge, and last a lot longer for backyard use as a result. The practical benefit? Ive done at least 20 sets of lugnuts on my vehicles, over the last year, on THE SAME, INITIAL CHARGE. Try doing that with NiMh or NiCd. What this equates to is fewer battery cycles, a tool that is always ready to go without having to think about keeping it charged, etc.
Score two for the IR - Li-ion battery
IR has a family of Li-batteries which all use the smart charger and can be swapped around. For example, I can use their big battery on their LED flashlight for a brighter beam and longer life, or i can use their smaller battery to run it if I have one available. I can use the smaller battery also to run an electric ratchet. It seemed to me (prove me wrong, but I didnt gain a compelling grasp that I was off) that IR has more parts that can be used with the battery/charger system/family than snap-on did.
Score three for IR - somewhat wider application of the battery system.
For me? The choice was IR. And it has been great. Far more power and ability to remove stuck lugs and bolts than my 12A milwaukee plug-in. Light and convenient with a great battery.
The only one that would be on my list at this point besides the IR is a DeWalt, IF and only IF it could be had with a Nano Li-ion battery. The iron phosphate chemistry used in those batteries is very attractive to me, and I'd be keen on using that, especially since the dewalt cordless system has a lot of good stuff...
So Id say the IR or go with dewalt for long-term tool choices with everything youll need around the house.