The answer is: "You should buy as large a pool table as you can buy, given your space restrictions."
Clear surrounding space is required for a pool table because cues are 58" normally and when you shoot a shot on the rail, your cue will need to be drawn back slightly. This means that you will need approximately 58-60" around your table in order to play pool unobstructed. Corners add problems, they don't take them away. In other words, if you think that there is more space because the room opens up from a corner, that is unlikely. Unless the room that it is opening up into is larger than the measurements below, the corners will still provide obstructions. This chart will answer some of your questions, but it is not the full picture.
Who will be playing on the table? For families with smaller children, a 4' x 8' table may be the answer no matter how much room you have. The long green surface of the larger 4.5' x 9' table will be daunting for children; billiards is a great game for your kids, but they will have more fun if they can reach the shots. There are also some great aids for kids like the Kid's Shark Guiding Wheel, available at our shop.
Kid's Shark Guiding Wheel |
Finally, if you've got obstructions like tables and chairs, don't worry, cues can go over and under these objects. A tall couch or a wall, however, will mean having to use a short cue for all the shots along that side instead of just a few shots around a post or protruding corner wall.
Even if you need to make a few small adjustments, keep these thoughts in mind when you are purchasing your next table and you will have many years of great play and entertainment.