I never prune, except to lift the lower branches away from the soil or to trim out weak/diseased stems/branches. My tomatoes are mostly of good size, generally have great flavor and texture. The plants produce early with first ripe fruit usually picked in the first of second week of May here in S.C., zone eight. If the plants don't die from disease, then harvest continues until the first frost in November. I do use a succession of plantings between the third week in April through about the second week in June. That way there are most always some plants in that early growth vigorous stage.
To each his/her own, but from my point of view, why take on an additional chore, when the plants already produce far more than enough top quality fruit over a long season? the only reason that I can see to prune and/or cull tomatoes would be to try and grow top sized fruit and for me that is not a desireable goal, as for slicers I prefer the 10-12 ounce size. Many of my slicers weigh in closer to a pound or more and although eaten with pleasure are not my top choice.