I have a Snap On flex head ratchet that is about 18". I think the model is RKRSX936JT but don't know for sure. I love it. It is long enough to give you enough leverage for most stuff, but not so long that it gets in the way too much. The flex head is stiff enough that it doesn't flop around without having to be locked. And I have put a long cheater on it which it handles no problem.
The advantage of the SHLF80 is the combination of a fine toothed gear mechanism with dramatically high strength. This is a first ever, best in class tool.
Consequently, I’ve found the length almost never is an issue, thanks to the flex and 80 tooth head. It’s a very easy tool to use and take advantage of.
Looking back over my many years of home auto repair, there are only a few
game changing tools for me. Impact gun is #1. The Snap On SHLF80A is easily in the top 5. I would choose this ratchet before buying any other premium ratchet due to the work you can get out of it.
FWIW, in no particular order, my other game changing tools have been: digital multi-meter/OBD2 scanner, LED lights, including head lamps, swivel sockets, ball Allens, swivel torx, high quality bit sockets in general, and really really good wrenches.
Socket quality, std ratchet quality, extensions, so often discussed, haven't been game changers for me. If/when I work in someone else’s garage, I’ll take my guns, the SHLF80A, and wrenches, speciality sockets for just in case. Everything else I can make do with.