[Brightcolours]

BC, the size and weight differences are profound! Register distance is everything -- no matter how "small" the D90 is, the Fuji X-A1 is less than half the size.

 

http://camerasize.com/compare/#483,179

 

If you shoot primes (like me) then there are a lot of tiny options for the Fuji too. Their latest offerings have been too big IMO except for the 35/2.

The D90 is not small, the D3300 is.

 

To make the assumption even more comical:

http://camerasize.com/compare/#520,448

 

Register distance is NOT everything, only with wide angle lenses.

 

Like I said, the weight difference is not overly dramatic. Sure, you can make combinations especially designed to make it look like the difference is huge. For instance, You can compare the FF Canon EF 35mm f1.4 L USM II to the Fuji X 35mm f1.4, and the difference indeed is huge.