At this point, I've worked with a couple. Most were from Kessler. My favorite is my current slider, a 2ft Cinevate Duzi 4 (Cinevate is no longer in business). I like it because the flywheel allows really smooth movement, the carbon fiber doesn't flex as much as aluminum, and the overall package is pretty lightweight in case you want to run it on a single tripod (tip: mount on a 100m half ball for significantly less tipping/dipping).
I just bought the yc onion hot dog bun. It's motorized and can go sideways into a vertical mode with an 11 lb payload, which is why I bought it. I haven't used it on a shoot yet but I like it so far. The fastest speed is not that fast, but I bought it to do slow, controlled moves anyway so that's fine. There is no flywheel so if you want to use it without the motor it will not be as steady as one with a flywheel