Is your chat text only? I think for media WebRTC is going to always win in the browser (unless you have the developers who can implement custom congestion control etc..)
For text only I still see a couple advantages
* E2E Security. With WebRTC I don't have to worry about snooping. Why should I upload my messages to a server?
* Scaling/Bandwidth/Ops Burden. Massively reduced if all my clients are directly connected to each other
* Ajax (TCP) can't do as much. DataChannels give me lossy/out-of-order messaging. Not useful for chat, but really great if building anything gaming/real-time
Yeah - I think all of that supports my point. Aside from security (which most users wouldn't be able to verify in any case) none of those things are relevant to low-traffic chat. i.e. "talk to our live advisors" or "collaborate with another user". The bandwidth and load is tiny and I can imagine handling hundreds or thousands of concurrent users with a traditional architecture and commodity hosting.
For text only I still see a couple advantages
* E2E Security. With WebRTC I don't have to worry about snooping. Why should I upload my messages to a server?
* Scaling/Bandwidth/Ops Burden. Massively reduced if all my clients are directly connected to each other
* Ajax (TCP) can't do as much. DataChannels give me lossy/out-of-order messaging. Not useful for chat, but really great if building anything gaming/real-time