I always assumed the rail version was more stable but I have no way to compare. I'm guessing the rail version is better though. I was planning to upgrade with the rail kit but never did. I bought this printer to do quick prototypes of items for clients. I soon found that I could order much, much better parts online as prices dropped and quality got better so I began using my printer less and less and never bought the rail upgrade kit. Now I just make parts for friends boats or cars now and then. It's still a great printer.

I would be curious to see what the current top rated do-it-yourself printer is. Maybe it's still the Maker Farm. I just haven't researched it.