It depends. Possibly for very small stumps.
I haven't used that grinder. there are others out there that use that same 13 hp honda engine. I would imagine that for small stumps, it would be acceptable to you. You might want to check around and see if there is one available for rent. It would be worth trying one out first. Make sure it has sharp teeth.
For what it's worth.... one of the main factors in efficient stump grinding is the spinning mass of the cutter wheel along with sharp cutters. Of course you need a big enough engine to keep that wheel spinning under load (as in cutting).
The Carlton 900 model you're considering will be lacking in this area. I don't think there is enough mass to that wheel.
In that price range, I'd consider an Alpine Magnum(do a search here and on Google).
This grinder also has a small cutter wheel. From what I can tell(keep in mind, I don't own one...yet. ;-) )
But the design of the grinder allows you to apply a lot of leverage. With the Carlton 900, you're looking at. All you have is the weight of the wheel to apply downward pressure into the stump.
I have never heard of the other brand you mentioned.
I would consider the Alpine Magnum.
Hope this helps.
Take care,
Mitch