In a local test on my PC, I could reach higher rates in HTTP-POLLING.
Are network roundtrip times involved in your test?
Or any elaboration time on the client side?
Otherwise, we think that you should have room for improvement.

Anyway, I must correct myself on one point.
A couple of posts above, I wrote that in the default configuration there are no pauses introduced by the Client or Server apart from <max_delay_millis>.
But, actually, the JavaScript Client Library also has a similar pause, which is also aimed at improving the efficiency; this pause is 50 ms; so, at the current stage, you are going to face an upper limit of 20 polls per second.

However, we acknowledge that your use case is getting increasingly important, so we are planning to remove the limitation since the next update of the Colosseo preview release.
In the meantime, we encourage you to obtain a limit-free version of the library by applying the following change to the current version of the library:
- open lightstreamer.js in a text editor
- ensure from the heading that it is Version 6.0 b2 Build 1525
- find the following string: if(this.Uv){var j=n.uC()-this.Uv;if(d>j)d-=j;else d=1}
- replace d=1 with d=0 at the end of the string