I used both but indeed i`m using AMD now. Also AMD is somewhat infamous for their stock fans.
I never really experienced any problems with multi tasking on the AMD yet. Quick side note i do not really play bf4(or something that much graphic consuming) and as well run 6+ clients. But for sure it should be doable.
Also i do have plugged in 16gb of RAM and just now by having only chrome, steam and skype open almost 4gb is gone. So i would recommend adding more then just 4gb is a must. (which is also favorable for the (on board) graphics).
Or this 2x means you get already 2x 4gb, then it might work out. Tho still for 6 clients and bf4 i wouldn't be surprised for getting performance issues.
Long story short. Yes they are good for multi tasking but its not only up to the processor.