You have UNREALISTIC expectations.
Plain and simple.
Either you need Chrome and the VAST amounts of web that only CHROME can give you or you do not.
Give us a LIST of these 150 to 300 tabs so we can inspect them ourselves.
I have a strong hunch that MyPal v27 can handle those 150 to 300 tabs better than anything "newer".
"Newer" is simply NOT always "better".
Throwing 300 tabs at an i3 - come on man, you can't be serious!
Disable ALL .js, disable ALL .css, disable ALL images, view ONLY the TEXT on those 300 tabs and you might be fine that way.
I'm with @Vistapocalypse "The solution is obvious. There is no need for 150 open tabs!" NOT ON AN i3 !!!
I'd be interested in seeing that list of 150 to 300 tabs so I can gauge for myself which browser can handle that task best.