Never buy LEICA 😉 - this cot more that GFX100S - and what is better, of course FUJIFILM.
Diff story is full frame VS crop - FF is everytime better, but monochrome sensor is not good, he only don't have bayer mask and all pixel is resolution and diff. calulation and no inerpolatin.
BUT: X-T5 have bigger resolutin, then make same, yp FF - modern SONY is better too.
But all is about PRICE VS Quality (+size and fun factor) - then GFX is price comp. - and GFX is winner in all aspect, only in size is bigger.
Fuji never make BW chip, because is useless and is possible all calculate, now we have CMOS wit no-low lowpass-filter, the is every-time sharper and better - and X-T5 - you have more datat that overexpensive leica - M - that don't have fix focus or Q - that have only one lens.