I play on 7' and 9' tables, however, my practice table is a pro-8 or oversize 8'. This table is a 1973 Gold Crown 8" by 4" short of a Full 9'. It's easier to adjust down in size than to adjust up, but the 8" less lenght and 4" wide difference I make up by triple shiming the pockets (mine are 4 & 3/8", corners and 4&5/8 sides). the pocket size helps for all sizes. When I play on different size tables it only takes a few minutes to actually adjust and your shot making will always benifit by the pocket sizes I practice on. I have found this size is perfect using these pocket sizes, howerver anything smaller will change how you play shape (and I don't think this is a good idea). Remember on most shots on larger tables your cue ball is into a roll sooner then a small table when it's still in a skid motion. It's not really sooner it's based on distances. So moving from one size table to another this is the most important thing to remember because it changes the way you will play position.
If you only play 9'ers then get a 9' if you play 7,8,os8,& 9' tables a OS8' is a good choice with the adjusted pockets. I have made a good living playing pool for many years and this has worked out well for me, because I play on any size table, even 12' round holes now and then. Hope this helps.