I had both for quite a while ( not at the same time though ) and there are some key differences :
Leica SL :
surprisingly compact ( viewed from above ) , much more X1D-C ethos of simplicity ( actually, its in line with the S medium format cameras ) but quite tall. AF is very much ok, specially with the 90-280 lens, bit less so with the 24-90 and quite slow with the 50SL. Problem is Leica very slow, very lethargic lens schedule for the SL : while the 24-90 is a great lens, for me, its nothing special - sharp, controlled, but… without "zing". Also, the whole package its a bit of beemoth. DR and High Iso is very nice, EVF is the best until today - super high res, marvelous to look at but quite slow when you are panning the camera. 50SL is a superb, full of Leica magic - but a slow beemoth. 90-280 is spetacular too, but my vote is for the 50SL - it is Leica's best 50mm, bar none. ( yes, that includes the 50APO ). Never had problems with mine, used a lot with M lenses, makes focusing with them a breeze and you can get some great results.
Fuji GFX50S :
surprising compact ( not tall at all ) but man, that hump in the back is huge. It is not a pretty camera AT ALL but its very functional. I'm a Leica guy all my life, so I get lost and a bit infuriated with so many menus and deep customizations. DR , Resolution and ISO are superior to the SL, no contest. EVF is ok - nothing special or to write home about, keep fingers crossed that they will release a higher mp viewfinder and then the camera would be perfect, afterall the viewfinder is modular. Now, lenses… bear in mind, I'm a Leica fanboy. I love Leica, I had Leica since the M8 was not even a dream. The GF lenses are nothing, but nothing short of spetacular - all of them. Their price is NUTS. Quality vs Pricing is out of this world - 110 F2 is just out of this universe - I've used Leica S medium format and the GF lenses are at the very lest as good or in some cases, better. 110F2 is better than 100mm Leica S. 32-64 zoom ? destroys the Leica S zoom, in every possible manner. 63mm is a very nice, compact lens - albeit a bit slow to focus ( no internal motor ) makes great images.
Unless you have a humongus M lens collection with exotics ( 50 Noctilux, 75 Lux & Nocti, etc ) and have dim eyes, the SL doesnt make sense.
The GFX50S is superior in every possible measurable way - apart from design. The GF lens are cheaper, better, weather resistant and draw sharp and gorgeous.
Leica SL :
surprisingly compact ( viewed from above ) , much more X1D-C ethos of simplicity ( actually, its in line with the S medium format cameras ) but quite tall. AF is very much ok, specially with the 90-280 lens, bit less so with the 24-90 and quite slow with the 50SL. Problem is Leica very slow, very lethargic lens schedule for the SL : while the 24-90 is a great lens, for me, its nothing special - sharp, controlled, but… without "zing". Also, the whole package its a bit of beemoth. DR and High Iso is very nice, EVF is the best until today - super high res, marvelous to look at but quite slow when you are panning the camera. 50SL is a superb, full of Leica magic - but a slow beemoth. 90-280 is spetacular too, but my vote is for the 50SL - it is Leica's best 50mm, bar none. ( yes, that includes the 50APO ). Never had problems with mine, used a lot with M lenses, makes focusing with them a breeze and you can get some great results.
Fuji GFX50S :
surprising compact ( not tall at all ) but man, that hump in the back is huge. It is not a pretty camera AT ALL but its very functional. I'm a Leica guy all my life, so I get lost and a bit infuriated with so many menus and deep customizations. DR , Resolution and ISO are superior to the SL, no contest. EVF is ok - nothing special or to write home about, keep fingers crossed that they will release a higher mp viewfinder and then the camera would be perfect, afterall the viewfinder is modular. Now, lenses… bear in mind, I'm a Leica fanboy. I love Leica, I had Leica since the M8 was not even a dream. The GF lenses are nothing, but nothing short of spetacular - all of them. Their price is NUTS. Quality vs Pricing is out of this world - 110 F2 is just out of this universe - I've used Leica S medium format and the GF lenses are at the very lest as good or in some cases, better. 110F2 is better than 100mm Leica S. 32-64 zoom ? destroys the Leica S zoom, in every possible manner. 63mm is a very nice, compact lens - albeit a bit slow to focus ( no internal motor ) makes great images.
Unless you have a humongus M lens collection with exotics ( 50 Noctilux, 75 Lux & Nocti, etc ) and have dim eyes, the SL doesnt make sense.
The GFX50S is superior in every possible measurable way - apart from design. The GF lens are cheaper, better, weather resistant and draw sharp and gorgeous.