Fuji X20 or X100s

The question is do you need a zoom or not

The X100(s) has a fixed focal of 23mm semi wide

It is mainly designed for street photography "à la Cartie Bresson" and lanscape

It supposes that you can moçve to go close to your target or on the contrary go to a distance for wider view

It has advantages : build dynamic perspective and disadvantages : need to move

Only can answer the question if this will fit your needs

In terms of IQ the X100 is much better thna X10 and probably X20 due to a better sensor

Very different cameras indeed

Another sensible choice would be XE1 + 18-55mm which is about 200$ more than X100S

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Good judgment comes from experience
Experience comes from bad judgment