Scott,
Did this yesterday while my other was here and held a pleasant conversation while it was cutting the cats.
Now that's a new use for the Shopbot i'd never thought of
I've used the router for 7 years and only until you get up into the 21,000rpm does it sound like it's screaming. Like others have said you buy a quiet spindle but put a loud dust collector in there and it defeats the purpose. But even then when you shut the shop doors and get 10 feet away it is just a dull hum you hear.
I would say a majority of what i do is 3d work that takes hours of cutting usually with small bits making only small amounts of sawdust. A majority of the time i don't even use the dust collection because i have the wireless camera setup to a side monitor and just watch it work while i'm inside watching football (DA..BEARS!)
What it comes down to is your budget and how meticulous you are. The spindle takes more maintanance and care in operation and a router you just turn on and go.