I’ve had 2 KSs and 3 Reverbs, tbh they’ve all been decent. I think the main wins…
Cable > hydraulic. Easier to maintain, easier to fix, and no significant downsides imo as long as you give it basic maintenance. I tore the cable off a KS in the alps, bodged it on the day so I could manually operate it, then replaced the cable later for £2. With a reverb I’d have been ****ed.
KS lever > Reverb lever. Not everyone agrees but I always think it says it all, that the reverb lever is best fitted upside down and on the wrong side, and even then it doesn’t play well with a lot of brakes. The thumb action is just plain poor imo. KS isn’t perfect but it can go in the right place on more bikes and that’s a fundamental difference. (I think people get obsessed with using teh lock-on clamp, which puts it in a pretty orrible place, but you don’t have to)
Reverb > KS on cost. I’d have got a Lev Integra but at the time you could more or less get 2 Reverbs for the price of a Lev.
Reverb > KS on travel. The 170mm Reverb is a real killer app imo.
KS > Reverb for parts. This one’s potentially quite big. A Reverb lever costs a fortune to repair. KS, the bits are sensibly priced. I lost a bit of the cable mech on my i950 due to a spannering error and I thought I was going to get dry bummed, it ended up costing me £1 😆 The chap was very apologetic about the £2.95 postage.
Reliability… TBH they’ve all been alright. Both my KSs were a little bit iffy from day one and needed serviced to fix them, after which they were great. The 150mm one which I still have, eventually needed a big repair but it’s very well used and Jungle sorted it quickly and surprisingly cheap- £75 for a “replace all the innards” service. Reverb, if you break it you tend to just get a new one. But how does that work out of warranty?
I’d buy either again. Just ordered a 170mm drop Reverb for the big bike.