I have a 120xp 1/4" ratchet and I've said it many times, I like it better than my Snap On T72. It is smoother and thinner. It also is a bit longer as I feel the T72 is too short for my man hands. I don't own an 84T, but always heard good things. The only thing I don't like is the 120xp's aren't made with quick release. Only 84T are. I will be buying one soon.
I'd say they're strong, but I would never put a ton of force on any fine tooth ratchet like this. The 120xp, dual 80, Maxx 88, etc. You need to know when enough is enough. Obviously a 3/8 would take more than a 1/4 and 1/2 more than 3/8, but I picture in my head all those self propelled toy cars I had as a kid. Eventually, I would play so hard they would break, and all the little fine tooth plastic gears inside would fall out all chewed up and broken. I have never had a problem with any of my newer ratchets, but as mentioned above, I know when to use a breaker bar.