If your planning on using a Dremel, either of those steppers will be more than adequate. I have almost identical ones in my pcb mill using a Proxxon spindle and I've used it for everything from machining timber plaques, to perspex and aluminium engraving. A 50cm x 50cm work area though I would consider more than a little ambitious for such small steppers, NEMA23's would be better suited for that size with a better spindle than a Dremel, which really is only tenuously spindle-like in reality (pretty crap in plain english).
You will be very limited though with what you can do. If your engraving you'll have no trouble, machining will be far more time consuming with slow speeds and shallow cuts.
cheers, Ian
It's rumoured that everytime someone buys a TB6560 based board, an engineer cries!