The QCX+ and QCX-mini are outwardly the same radio in terms of features. For SOTA, the QCX-mini wins, due to the lower current consumption and smaller size, also the form factor is more trail friendly.
The MTR is a very nice rig, but quite expensive and many users complain about low audio. I have kit built MTRs and I use 16 ohm earbuds with good sensitivity. Cheap earbuds might not produce enough audio. I cut my teeth on MTRs, having firstly built an MTR-2B in 2012. I built my last MTR in 2015, an MTR-5B. I learned to use the MTR keyer timing and I am comfortable with it. However, when I swap to other rigs, like FT817, I struggle with the keyer timing. Having talked to some folks, it seems as though the MTR keyer timing is a bit ‘funky’, the other rigs are more ‘correct’.
I have no problem with the QCX keyer though, and there’s many options for keyer timing too in the menu. In terms of features per Dollar, the QCX has the most favourable ratio. The only negative with the QCX really is the lack of a multi-band option.
I wasn’t keen on the HB1B, but I know plenty of people who love them.
If I had to keep only one of my SOTA radios, I’d opt to keep my KD1JV MTR-5B, it has a display, auto CQ, 5 bands, takes about 20mA on receive and weighs only 160g. The LNR Precision MTR-4B is a close relation with a few more features and one less band.
I can’t think of any more CW rigs, except perhaps the ME+ radios, but they’re old fashioned by today’s standards, having an L-C VFO and only up to about 2W output. The SW+, which was the original version, seemed to be a popular choice as SOTA was just starting out about 20 years ago.