Your problem might be disk IO speed related. How fast is your storage? Most browsers still do trash a lot of disk IO even if you have plenty of memory available. For whatever reason it seems like OSX is way more prone to having performance problems due to slow disk IO. I have plenty of RAM, CPU and GPU so whenever I see a performance hiccup I know it's time to clear some space off my SSD. Performance of my (several year old, third party) SSD goes off a cliff when it has less than 15% or so free space available. If I get it back to 20% free space it's back to smooth sailing again.