Hi Steve,
As a long time cyclone owner - why not a cyclone? Single stage DC's lose suction as the bags fill up so that max CFM is a pretty worthless number after they start collecting dust. Sure, you can overcome this with more HP and if you vent outside, but you will be pulling your warm/cool air out of your shop! I am not trying to sell you anything but your pipe and fittings can easily run you $1,000 to $2,000 and a 2 stage unit really is not that much more when you factor in all of the costs and they are infinitely more efficient and they are specifically designed to handle long runs without modification(s).

I think the question many of you should be asking is - can you afford to do your system over again in a few years? If yes, unquestionably go with the 3HP unit. If not, save a few hundred more and get a cyclone. IMHO, this is one of those tools, like a table saw or jointer, where bigger actually is better.