Pixelization WebGL(PlayCanvas) output in some browsers

Pixelization WebGL(PlayCanvas) in some browsers.
(for example, in Firefox, IE)
I noticed a bad thing.
In the Chrome browser, the application is displayed smoothly, but in Firefox with a small pixelation (especially with a small output window than in full-screen).
Also, the application runs slower.
Because of this, we can not deliver the project to the customer.
Perhaps the problem is still in some other browsers.
(Safari / IE / etc.)

Please tell me what could be the matter (is this a very important question for us)?