I have the older discountinued Makita LXT (green & black body) impact driver with the large capacity batteries and the Makita (white & black body) impact driver with the smaller batteries.
I bought the smaller white impact because I needed an impact for a quick job out of town and didn't have my older Makita.
The MAJOR difference I can tell is the difference between batteries. I can generally get 3~4 times the driving time off the larger batteries compared to the smaller ones. Outside of that, I have driven 1/4" x 12" timbertech lags without predrilling and neither impact bogged down until the battery was dying. Grabbed another battery and went on.
When I was working as an electrician, I had a coworker that had the complete LXT set. He was terrible about leaving his batteries in the truck at night and his batteries wouldn't hold a charge after about 2 years...
I have used mine almost EVERY day for the past 7 years and they are still running strong, but I have NEVER let them get cold unless I am using them. Having them out in the cold while your on the job is fine because they actually will maintain a safe internal temp (as I understand it) until they no longer have a charge.
I also charged my batteries every night while using them. When I stored them long term, I drained them to about half capacity and left them and then charged them about once every month or so and then would drain them back down a bit.
I find the Makitas to be pretty bulletproof. About 6 months after I got my first impact, I dropped it 20' out of a scissor lift. My first thought was that I had destroyed it, but after getting down off the lift, I found that it dropped directly on the bit holder extension I had on it, which bent the hell out of the holder and took the brunt of the force, leaving it completely undamaged outside of a few scratches on the rubber and plastic, as well as a few scratches on the battery.
