Thanks for all the responses. I should have mentioned that the reason I am looking at these two machines is that I have a low arched doorway, and these both fit. A VF will not fit unless I remove the ATC, which I would rather not deal with. Also, I have limited space, so I will have to limit myself to a single VMC.
My immediate application is an assembly of 12 parts, aluminum. With a 5k spindle I spend about 40% of time machining with EM 3/16 or smaller, and about 15% of time surfacing. I plan on fixturing 20-24 parts at a time. I am guessing that a 15k spindle vs 12k spindle will save me around 10% of time, but I haven’t done calculations. I will be using this machine for other jobs, so a faster spindle will just offer some more flexibility in the future. The truth is that both machines are a huge improvement over what I am using now, and I will be happy with either. I have looked at some used machines, but since this is my first ‘real’ machine, I’d rather pay a bit more for some piece of mind. I have to say that the folks at Yamazen have been very responsive and I get the sense that I will receive great support. I am sure that the same would be true of Haas. What it may boil down to is 40 vs 30 taper.