The choice is easy for me, lately I always buy Xeons, or maybe an i3 (yep, supports ecc) if only 2 cores are needed. You get every feature then at least, thanks to the price fixing ecc is barely a premium anymore. (but damn ram is retarded right now)
VT-d is only for pass through which 99% of small VM users don't use but 98% confuse it with VT-x and EPT
Honestly having expansion cards support SR-IOV is better than VT-d for the big clusters.
Funny enough, if you don't need to overclock a lot of desktop boards support xeons and sometimes they are cheaper than equal or slower locked i5/i7 models. (unless you live near a microcenter, then the consumer models w/ bundle pricing win every time)