Bulls are meaner than Dingoes
We use a Toro combination loader / stump grinder. The heads are readily interchangeable. It is a pretty effective mid size unit for metropolitan work. We only use it if we have to as our primary function (arborists) pays a much higher hourly rate than stump grinding. For really large stumps or exclusive stump work we sub out most of the work to a specialist who has three machines of varying sizes.
We chose the Toro because it has the same power plant as most of the competition (a 22HP Kohler). It's real advantage is that it is 856mm wide with either bucket or stump grinder head attached. This is pergect for fitting through most garden gates. As a loader it can lift 250kg with ease which is handy for those big blocks that won't fit through the chipper. It runs on tracks instead of chain driven wheels and this reduces the maintenance problems associated with chain drive anything.
It performs reasonably well on most stumps we do but I stress we do not run a stump grinding business. It is good for the occassional stump job and the versatility to be able to pick up big blocks is a bonus. We are actually modifying it to put a standing plate on the back so that we can counter balance bigger weight than 250kg. The Hydraulics are more than capable of handling this weight but the machine only weighs 750kg so it can get a bit uppity on the fron tracks.
Good Luck