We owned many machine from Babolat, Wilson and Tecnifibre. I believe the best system or rail system we used was the Tecnifibre straight rails. it was very strong and firm. Silent and Smooth. The base clamp was on a guided rail which I believed made it strong and solidI was just about to ask this question, but thankfully used the search feature. Babolat has used the semi circle design in previous models with the Star 5/Sensor designs, but with their newer Racket Station model they have gone full circle...figuratively and literally!
Having strung on older model manual and electronic Gamma stringers for so long, I have only known straight rails...but even Gamma's latest models have gone to a slightly curved rail (not as extreme as Babolat). There must be something more to it than just "cool looks" and it's certainly has survived through "it's just a fad" design stage.
I recently strung on a Babolat Racket Station at a local tennis shop to me, and I found myself a bit clumsy navigating with the circular rail system. I loved how smooth the base clamps were moving on the rails, it was effortless...and I love the push down base clamps as well as the self adjusting string clamps. I am sure the curved rail design is something I could get used to over time. For now I am fine with my straight rails on my old and trusty Gamma 5800 Els.
My thoughts are that the curved rail design better follows the shape of the racket. As head sizes have grown larger through the years, the stringing area has grown "wider" thus a curved/wider rail would make stringing, in theory, incrementally "easier"?
Just my $.02...and I would love to hear other thoughts on this? Especially from those of you that have used both the straight and curved rails...ideally, for me, it would be someone who has used the older Gamma 6004 with straight rails and then switched to the newer model with the slightly curved rail. For the most part everything is relatively the same so the difference would just be the rail and I would be curious if they were able to string faster, with less effort or more efficiently on some or all types of rackets. Or maybe the design was more to be able to make stringing other sport rackets easier (racquetball, squash, badminton, etc...), which would completely contradict my theory of making it easier to string wider rackets.