Which browser?

Safari, because of:

1. iCloud integration
2. Security
3. Speed (thanks to NitroJS too)
4. Battery life.

 

Firefox

Slower in benchmarks blah blah, but for the power of its extensions which I find invaluable and essential it's still the best, plus with every other computer be it Windows, Linux never mind a Mac for a cross platform user like me it's sync knowing your data is not going to be mined is also top notch. With cloudy tabs for OS X I can have the iCloud bookmarks too.

Chrome has its uses on OS X - for flash! Safari occasionally gets used for the keynote video streams

 

Safari! 'Cos I didn't try the rest on my Mac. Safari runs ok so pretty happy with it.

Running Firefox on my windows machine though (giving me some headaches as flash constantly crashes).

 

Safari and Firefox.
Safari is fast and the integration is amazing but ive always used Firefox and it has a nice refined feel to it despite being slower and the pluggins etc.
Its handy having 2 browsers for multiple accounts on the same site ie Paypal, Ebay etc.

 

I'm quite happy with the safari on Yosemite. Was using chrome since about five years ago when Firefox started losing its way.