Earlier quoted context omitted.
And inherently a far less ram using browser. I do 500 tabs in under 3GB. By also not implementing all the useless attack surfaces like DRM, Integrated PDF reader, WebRTC, and friends it avoids many of the exploits which make modern browsers like FF and Chrome insecure. Overall it probably balances out. Especially since PM users are likely to have JS execution disabled by default (like I do).
It's pointless to say things like "500 tabs under 3GB" without knowing what's loaded in these tabs.
And 500 is just my actively loaded tabs. I have another 500 suspended.