From my past experience with Table Tennis Balls, I've came up with two favorite brands to buy TT balls from for training purposes. The first brand is butterfly although I've only had 2 batches of balls from them, IMO I think there training ball suits my needs the bests. There's many different aspects that can nominate this being a better ball than other balls.
The first aspect is the pricing of the balls, surprisingly these balls are relatively cheap compared to other Butterfly branded TT balls. The last time I ordered was from Sports Authority, it only cost me 34.99 including shipping (There was a promotion at that time)! This is a good deal since it divides down to about .50$ per ball.
The second reason is the quality of the balls. Although I have to admit these balls come no where near tournament quality balls, but they exceed the requirements to become a usable training ball. There's no "ball seam" that runs in the middle, although if you look VERY VERY close you can seen the "seam". You barely feel it though, so that isn't much of a problem. The bounce is good and very consistent compared to other cheap training balls. There was not a single ball that was misshaped in both my orders, this shows how excellent QC is.
The final reason I would like to share is the packaging. The balls come with a Medium Duty quality clear plastic carrying case. For this low of a price, I think that it's amazing that Butterfly can some how manage to include a carrying case and still make some profit. Here are some pictures I took.
Picture of the Logo

A bunch of Them

The Carrying Case

Sincerely,
-Acer800 (John)



