The ones that go the furthest!

I've heard that any that are made in the US are the best.

Ball selection can be more complex, but for raw distance, you might want to start with Velocity.

but I think that ProV1 is better than ProV1x

I agree. Best bet is to get a sleeve of each of the Titleist offerings and put them in play.  If you play alone, play a couple different for each shot and see which one you like the best.  There's no science to it....just gotta find the one that suits you best.  I'm a big fan of the Pro V1 and the NXT Tour.  

How long is a rope?  

That's a pretty broad question you are asking.  You really need to figure out which ball is right for you and your game. 

Try the fitting tool to see what it says.  http://www.titleist.com/golf-ball-fitting/

TT

Good advice TT.     It's a good start Edward.    Side by side comparison works well.  A Titleist ball fitting is a great idea also.

Good Luck choosing your ball.

Deno

ProV1 for more spin. ProV1x for less. Two best balls in the game. I almost always play ProV1x, but occasionally due to either course conditions or the type of course I am playing, I will play ProV1's.

As long as you go with the Titleist brand you can't go wrong!

Just left a "fitting" with some guys from the Titleist Van. They told me that all of the balls are about the same length. Club head speed is a big factor as well as "feel" The Pro v's are the best that you can get. The main difference as I was told is that the v1x does not spin as much as the v1.