For highly threaded work that can use six cores, AMD Phenom II is probably better for low budget systems and Intel is better for mid-high budgets.
Need to realize that Intel will use less power, but for six threaded performance, AMD wins in the sub $300 USD market. The cheapest Intel CPUs that competes in highly threaded performance would be the i7s and they aren't really cheap. However, AMD has no competition against i7s and i7s aren't too expensive for their performance.
If you want to spend less than $200 on the CPU then the 6 core Phenom IIs are the best option, if you want to spend around $200 then the FX-8120 is the best option, and if you want to spend around $300 then the i7-2600/2600K is the best option.
If you were willing to spend even more than $300 then you should look at the i7-3930K, Xeons, and Opterons.
I have no idea what performance level you need nor how much RAM you need, but that's a run-down of the processors by price and performance for highly threaded work.