The one you linked to at e-bay seems to have more cabin space (longer coachroof?) and an inboard diesel engine. That extra weight and dragging the prop around will probably slow it down some, but a diesel is generally nice to have.
I believe this is the difference between a 'Marieholm 26' and the Marieholm 'IF Boat' or International Folkboat. The IF Boat has a large lazarette locker behind the cockpit where the outboard motor well is. I have never seen a M26, but from the eBay pictures it looks like they removed the locker, shifted the cockpit back and had more room for the cabin as compared to the IF Boat.
I have a 1976 IF Boat that I bought in VA. and sail out of Havre De Grace. I love the boat and sailed all winter long in it last year. I just finished my first solo trip from HDG to Baltimore two weeks ago. Many weekends I pack the tiny boat out with 3 or 4 friends for an overnight trip. True, its not the fastest boat, but the admiring looks for other sailors, and the "hey, what type of boat is that" questions make up for it. I have an ASym sail that works great in light winds (I think it might even be a used Lightning Spinnaker) I plan to take mine to the Caribbean in the next 3 years or so.
This one looks like its in really great shape.