I have not used a Sulky/Velke, so...... what do they have over a ProSlide. I guess if you have not used a ProSlide you cannot answer as well as those that have. That said, what I like about the ProSlide: Great stripes! You are doing to the grass what a striper does. No flat tires. No tire ruts. Folds up by it self, just step on/off. Permanent attachment. No hook up each yard. Use it or not, doesn't matter because it is already there. Easy to back up, no jack knife, I just take one foot of to remove a little weight... As cheap on or cheaper on E-bay (usually) Standing (I feel) is easier and less jarring than sitting, esp. w/o a suspension system of some sort. About the only thing I do not like: Not careful you can bust a shin! Dog waste you run over, avoid it by paying attention like you should be anyhow.... So what's the advantage to Sulky's?