Linux trunking, bonding, and bridging is outdated, awkward to configure, and doesn't do vlans or virtual interfaces very well. With today's modern infrastructure requirements, I think proxmox 4 should switch to openvswitch by default instead of legacy software. It does everything that the other three do, it does it with a simpler to manage interface, and it does it in one unified package. Not only that, any moderately sized data center will need these features to be properly configured anyway. Having them set up out of the box and ready to go can only help.