Honestly Chrome is the worst. I'll have 10-12 tabs open (including apps like Asana and Gmail, plus a few extensions) and it takes a while to switch tabs, especially when I'm also doing development work, with Atom open, a few iTerm tabs, Activity Monitor, Finder windows, Messenger, Telegram, and Mail. Add a few daemons for servers or databases running in the background it just locks my system up.

Plus I work with data sets, and my HDD is filling up fast...

For me it was the 15' haswell rMBP's that did it. Quad core i7, pciX ssd, that screen, amazing battery life. Literally the best laptop ever made.

I just wait for nothing now. CS and Xcode were super annoying on my old machine