Yeah they'll wear the sheath more, but even in-spec ropeman1 has been observed to sever rope sheathes (and at slightky higher loads complete ropes)as low as 4kn. Toothed ascenders still strip sheaths, but at a bit higher load.Maybe, but I read somewhere in a review or something that they tend to snag the rope fibers and eventually damage the rope. My 1's grip the rope plenty reliably for me. I've never had it threaten to let the rope slip through. Pros and Cons to each, I suppose.
If there's a grip difference it would be on a gradually loaded taught rope.
I don't find ascenders especially useful except for ascending rope (or hanging a deer i guess). also I'd probably never run a rope that a ropeman1 would be in spec for anyway.