The way I look at it, not having an electronic compass and altimeter makes no difference in the field whatsoever. You should be carrying a decent compass for backup anyway and electronic compasses just don't work very well. The altimeter might be more useful but providing you have a proper topo map uploaded on the memory card you'll be able to take pretty accurate altitude readings based on your position. Probably more accurate than the built-in altimeter in the Vista could provide.

The Legend HCx is just a great unit. Not having the unnecessary bells and whistles is no setback in itself, it only means the battery life will be that much better.