It would be based off of you club head speed. If it is sub 105 on average you need a softer ball for distance. It's all about compression, so it depends on your swing. I am a big fan of Vice balls, and they have a fitting tool on their website that might be worth checking out. The price points and performance have been great. Personally I'm in the 110-115 range so I use the Pro-plus and that works really well for me distance wise.
Also, I haven't tried them yet, but Maxfli just came out with a tour ball that has been picking up traction lately as being a really good ball.