Updating browser, or upgrading OSX?

I have a Macbook Pro. It came installed with Snow Leopard 10.6.8. It seems to run fine, though
I have been tempted to upgrade to new OSX's in the past. I really dislike the newer two dimensional flat
appearance of the dock bar. That is actually a major reason for not upgrading.

However, for several months websites have locked me out because my browser is not updated. It was last updated in Nov. 2014 to version 5.1.10. Apparently I can't update any more unless I purchase an upgrade to Snow Leopard (which will probably only update my browser), or upgrade to a newer OSX.

Besides my "appearance" issues with the dock, should I just jump into the latest greatest OSZ (el capitan), or pay to update snow leopard?

 

really, so i can return the dock to appear like snow leopard after downloading el capitan? i've read of people complaining in the past of the flat appearance of newer osx.

and, is there any reason really to stick with snow leopard?