The C3 1/2" impact was rated 300 lbs Ni-Cad or the regular lithiums. It is rated 325 ft/lbs with XCP packs.
The Kobalt 24v is rated in "nut-busting" torque. Whatever the hell it really means, it is always a much higher rating the the maximum working torque rating. That being said, I've used that Kobalt, and it is a hoss. It does have a lot more power than the C3 impact, but it is also huge. It's a lot bigger and heavier than the C3 impact. I do like that Kobalt and really all of Kobalt's 24v max tools are winners, but it's worth mentioning the size. Kobalt sells a baby 1/2" with a lot less power.
Like our C3 stuff, most of the Ridgid 18v tools are Ryobi tools. That's why the Craftsman C3 ID2030 1/2 impact, the Ryobi P261 1/2 impact, and the Ridgid 86010 1/2 impact all look identical except for colors, (and all share the 300-325 ft/lbs rating) is because they are basically identical. The part numbers for the internal parts like the motor, hammer case parts, etc are all the same. TTI/Ryobi is now making the 86011 for Ridgid. It is a slightly larger and brushless version of the 86010 and is rated at 450 ft/lbs. They have been selling it for over a year now. I have not used it and cannot comment on if it's really more powerful. I imagine it is. I'm surprised they still have yet to release it as part of their own Ryobi One+ line. I suppose it's only a matter of time.
That Craftsman V20 is a rebadged DeWalt DW889 1/2" (Stanley Black and Decker owns both Craftsman and DeWalt). It is rated 400 ft/lbs in DeWalt Yellow. It is terrible. One guy in the shop has one and it is weak. He use to work next right to me and I would get mad when he would continue to hammer on bolts with that hunk of **** just failing to bust them loose. He'd sit there and continue to make noise hammering away when it clearly wasn't working. The C3 has noticeably more power. The C3 is also a lot smaller. The DeWalt 20v line has since replaced the DW889 with a brushless version. My brother has it and it is more powerful than my C3. But that V20 tool is a joke. The entire V20 line is garbage.
The C3 1/2" impact is really not a bad tool despite its age. It is fairly powerful, and not overly huge. Yes, there are better ones, and yes, it would have been nice if C3 was still being made and we could get our version of the brushless 450 ft/lb rated impact, but I can live with the ID2030.