The things that I would consider are the rigidity of the design, the ability to be realligned should that be required, the size of the maximum print that you want to project on the baseboard. I would opt for either a color light head or a variable contrast light head considering that graded papers will probably continue to decline in availability. Both of these light heads will allow you to print on variable contrast paper. There are a number of excellent enlargers. I happen to favor the Durst for my large format condensor and Saunders for my large format diffusion enlargers. I have used the Omega C7670XL for medium format.
Originally Posted by zinzin
Also of great importance is the enlarger lens. Typically you would use 80 mm focal length for medium format and 50 mm focal length with 35 mm negatives.