One thing for sure, You cannot play x-outs in a tournament but you can play balls marked "practice".

x-outs prolly have paint defects maybe balance issues also.

cheaper price and cosmetic and or physical blemishes on the xouts.

Hi LFX, there really is no difference. x-outs have minute physical or aesthetic blemishes. i'd recommend practive balls over x-outs because they have only minute aesthetic blemishes such as an improper ink drop or something of the sorts. neither x-outs nor practice balls will feel nor play any different than a standard prov1. but they will be 10 to 20 dollars less. If you were looking to buy them i'd say go for it it's worth it. I hope this helps -Sam D

Mike D. (Team Titleist Manager) did a great job clarifying this on a previous post:

http://www.titleist.com/teamtitleist/team-titleist/f/5/p/9495/43209.aspx#43209

How do I purchase x-out golf balls and how much do they cost?