I have run experiments with various combinations. With a high duty cycle and a dirty environment, steel wheels on bare aluminum start to wear the aluminum over time. The wear looks like a general rougher surface, that looked like streaks, to the aluminum with the occasional pitting.
I set up a test fixture to test steel wheels on hardcoat and it ran non stop for 2 days. It was a clean environment, but I saw no notable wear. The carriage was loaded to about 20 lbs with 4 wheels, with the load sideways, like the camera slider.
My plasma cutter is intended to use hardcoat. The current version is just a half scale version and I expect a few other changes, so I decided to prototype it without the hardcoat. I don't have a lot of hours on it yet, but there is really no wear to speak of yet. Once the design is stable, I do plan to get the rails hardcoat. It think the hardcoat might be more robust to the plasma effects.
I know a lot of people who have made DIY CNC routers with steel wheels on aluminum angles and they held up pretty well. I saw one that was over a year old. It had quite a bit of scratching and pitting, but owner said he could not really notice the effects in the work it was doing and did not plan to rebuild it at the time.
Cutting would be best on a cold saw...
A cold saw might work better because of the slower speed. My cold saw has a high speed steel blade, not carbide. The blade cost about $150, so I am not excited to do any testing on it.
I think the damage to the blade occurs when you bare down on a flat supported surface. The sides and back probably do a lot less damage. The orientation of the part while being cut could mitigate the damage to the blade.