Just relating my experience. I am using a HEX (RB750Gr3) purely as a vlan enabled switch in my production environment.
I had a choice to use bridge vlan (no hardware offload) or switch chip vlan (hardware offload). I was concerned that using bridge vlan would max the cpu (and reduce performance). I didn't have to worry.
In the HEX using bridge vlan (no hw offload), 50 Mbps Rx / 10 Mbps Tx (real world condition) on the uplink/downlink ports (minimal traffic on the other ports) pushed the cpu to a max of 5%.
My conclusion, if you are thinking of using this product (or those with better cpu) as a vlan enabled switch, keep it on the bridge, there is no need to engage the switch chip (although its nice to have the option).