I have not used a Mark II, I have a IIn and a 1Ds II.
I believe the LCD screen on the IIn is larger, and it has a larger buffer. The transfer rates for an 8mp body are blistering when compared to today's large files, a real plus when in the media center and meeting deadlines. I have printed 16" x 20" and have no reservations about quality.
The interface on both is old school (everything is a two handed operation) but I got used to it very quickly, and transition between my 7d seamlessly. The 1 series are built like tanks and I really like the weather sealing.
I think you would like either body. The IIn is a fun camera, if you can swing the extra cash I would go that way.