I'd say the main difference is more that on a VM you "may" have other vm consuming resources of the host, thus the proxy being limited. But you can setup a resource pool for the proxies and set reservation for both cpu and ram so that you have all that you need. For the network, the same idea applies, there is other VM traffic going over the same uplink, regardless if dedicated vlan are used, but you can solve it a bit for example using NIOC (if your vmware license allows it).
Also, you may want to have some DRS anti-affinity rule to distribute the proxies over multiple ESXi hosts to spread the load over your cluster.
EMEA Cloud Architect @ Veeam Software
Veeam VMCE #1