KEB make pretty good stuff, but I haven't bought in wuite some time and can't say how good delivery is. Pricing is competitive with Hardinge, perhaps better than S&M.
http://www.kebkollets.com/
I've have some "experiences" with quality of the "super precision" guide bushings from S&M, but in fairness, they have always made good if there was a complaint. Hardinge has had exceptional delivery *and* quality with their fair pricing.
As for steel vs. carbide, I'd always choose carbide because it's easier to save a galled one should that happen. If you have older machines without a PLC or CNC-controlled bar feeder, this can be a common failure when the pusher hangs up. No end-of-bar signal trips = galled and/or smashed-up GB.