Rod has some great advice there, if you are buying new, go single phase every time when its available. The reason I set up a 3 phase system in my garage/ shop is that I like Euro Machinery and am cheap..
3 phase is a personal choice. If you are not sure you want it, you probably should wait. I enjoy getting used 3 phase machines at steep discounts, if I decide I don't want them anymore, I can sell them off and not take a huge loss.
Recently I picked up a very clean 2007 Felder Edge Sander with a 4 wheel Felder Feeder ..
Its 4 hp x 220V Ph3 with an additional 1hp x 220V Ph3 power feeder.. I got a great deal on it and have had a few cabinet makers offer to buy it from me as its a bit of a rare machine and a new one is the price of a low end car..
If your the kind of guy who is looking at the used stuff then a 3 phase set-up makes sense.. I would still not buy a new machine in 3 phase unless it was simply not available in single phase.. The reason is the same reason I have the 3 phase set-up.. The resale value is not nearly as good because its such a small market, and your relying on another device ( converter ) to keep it running..
I have never had any problems with my converter, but if it stopped working tomorrow, I would have 3 machines inoperable until it was fixed..