M50 vs M6 mark ii vs 90D vs eos RP photography mainly

Been there, done that. Holding my 70D in front of me just to get the best AF for shooting persons wasn't a great handling experience for me.

Neither is doing the same with an M6-II

as the M6-II but with EFCS so no shutter shock , it uses his existing lenses without an adapter,

OP can use the existing EF(-s)lenses with adapter on M, while you can't use excellent ef-m lenses on the 90D.

there aren`t many excellent M lenses and unlikely to be any more , the 11-22 and two primes are about it and they`re replicated in EF / EFs many times over in Canon and 3rd party ..

That's definitely not true when using Live View mode to get the AF you want. So with the 90D you get either bad handling and good AF, or good handling and bad AF (bad = no sufficient face and eye tracking across the frame).

I`d say shooting a 90D from the LCD is a lot more stable than an M6-II , neither have IBIS but the 90D has a good solid grip . of course there`s the EVF option of the M6II , the one area where it wins, apart from pocketability with a prime , as I say I think they ought to have made the 90D OVF-less

That's only an advantage if you're allergic to adapters

adapters make EF lenses even bigger

. For the rest it's a disadvantage, as pretty much all ef-m primes are better options compared to their ef-s counter parts.

All three of them ! (and one of those is a pretty useless slow short macro lens)   --  there are endless superb EF/EFS Primes in canon and Sigma , the guy may not even want to use primes anyway .

- no compatibility with the stellar ef-m mount primes. Note: the best crop portrait lenses are amongst these ef-m primes.

Above - endless EF mount primes from bargain cheapos to full on Pro level L s . there isn't a single decent standard zoom for EF-M, not even as good as the cheapo EF-S 18-55 STM  - you have to use the 11-22 and crop to zoom so natively its that, primes or a clumsy setup with the adapter with an EF lens on ......

- no mirrorless AF across the frame (at least not without awkward handling, where weight and size aren't a benefit at all)

they are for Stability and the 90D HAS EFCS so you`re not forced to use the wobbly E-Shutter when using lenses with IS built in

Just giving the 90D a fair shout here for a guy with EF glass who's used to using a DSLR instead of something which handles more like a G3X with a lens mount .....

believe me there's nothing I'd Like more than Canon to make a native 15-80 F3.5-5,6 which is as good as the 11-22 and put EFCS in the M6-IIs firmware (canon cripple hammer tactics there I fear) , or better still make an M5-II (with IBIS as well ) but they haven't yet and likely won't  ..... I Liked the M cams I`ve had very much but canon refuse to stop starving the system of glass and refuse to stop crippling the things and lineup