I always used to play with
Slazenger Wimbledon Ultra VIS Tennis Ball - 4 Ball Tin. But in recent years they really do feel to be much worse than they used to be (I have a theory - see below). So I have been looking for a ball that lasts a good while and is good value. Some people speak very highly of the
Micro X tennis balls (4 ball tube), but £21.99 for 4 balls is just too dear for me. I have tried Wilsons and Penns but have found the Head ATP to be the best of the lot. They feel good straight out of the can, but do seem to last longer than any of the others. Brand new Slazengers are still preferable, and if, like Wimbledon, you change them every seven games, use them. But if, like me, you need to get weeks out of them rather than minutes, you can't really go wrong with these.
(theory about Slazengers: the bloke in my local sports shop says that when the man behind Sports Direct bought Slazenger, he moved the manufacturing to the Far East and removed two layers of felt from the balls to save money. And that's why they don't last anymore. it could be rubbish, of course, but...)