I wonder why everyone is so keen on trunking 4, 8 or even more ethernet ports to one VIF. Having more than 2 links active at the same time makes no sense in >90% of all use cases as you won't be benefiting from the increased (theoretical) throughput because almost everything you do is I/O bound and I/Os scale with number of disks ,not the network, and that's the bottleneck in almost all cases.
Anyway, as the others already explained, you can only do VIFs on one controller and you should do single VIFs if you have multiple switches connected (i.e. one single vif over 2 multi-vifs with 2 ports each)
-Michael