Most Boeing guys are thrilled by the sophistication of the avionics apart from the autothrottles; Airbus guys are amazed at how basic it all is. Beyond that no problem at all!
Two separate type ratings -
CL600 covers all 600 & 601 variants with no differences training required despite different engines, electric system, bleed air system and fuel system across the variants
CL604/605 covers those and the 650; differences required between 604 & 605/650 despite it just being an avionics upgade, familiarisation for the 605 to 650.
It's mainly about the differences in the job rather than the equipment.