I would say that in the back is where you would have a greater chance of not having anyone next to you, but lately they jam pack those darn flights

I just flew SW coming home from our trip in August, and boy was I excited to see the exit row available, but then way disappointed to learn that you can't sit in that row with a belt extender

The flight attendents were surprisingly nice about being discreet when giving me an extender, but boy was I nervous that they hound me about needing that extra seat. I was very well prepared to argue the fact that my armrest went ALL THE WAY DOWN LOL!
Wow, where was I going with that

Basically I was going to say that if you can fit into the seat without an extender and the exit row is open, TAKE IT. There are only two seats in the row, with plenty of room!