The answer is really it depends. I know that doesn't help much but it really depends on the software and how many VMs you are going to be running. Hyper-threading is not anywhere close to the performance of a full core on the Intel® Core™ i3-3220 but the single core performance on the Intel Core i3-3220 is really much better than a lot of processors out there. Here are some nice benchmarks to help you see how and when these processsors excel. http://www.anandtech.com/bench/Product/675?vs=677
I would prefer the A10, 4 real cores @ 3.8ghz v 2+2 @ 3.3ghz, overclock the A10 and give each VM a minimum of 4GB and 4GB for host OS. Yes I know the i3 at a lower clock speed can go head to head with the A10, butthe A10 I believe performs better in multi-threaded tasks, which will suit VM's.