If all suckers are removed, the potential yield of a tomato plant is limited to the number of flower clusters that are produced along the central stem, the number of flowers on each cluster, and the number of flowers that set fruit and don't drop off. If a particular variety produced clusters every 12 inches, starting 2 feet off of the ground, an 8 foot plant will have 6 flower clusters; for larger fruit varieties, 2-3 fruit set per cluster, so that plant will yield 12-18 tomatoes. If you allow a second sucker to grow, it doubles the potential yield...and so on.
Removal of suckers will reduce the complexity of a plant, allow better air circulation, and so possibly reduce the incidence of foliage diseases that tend to be fungal in nature. However, people who cage tomatoes typically remove no suckers at all, leading to very high possible yields. It really all comes down to how you grow the plant (cage or stake), how closely spaced they are, and how disciplined you are with sucker removal, since they appear very quickly and can lead to an out of control plant in no time. Typically I don't remove suckers, but use twine to tie all growth to the central pole every 6-12 inches. This year I am going to limit all of my indeterminate plants grown in large containers in the driveway to two main stems, since disease was a real issue for me last year.
Determinate varieties should not be pruned at all; the various branches of the plant end in flower clusters and a very concentrated heavy yield is produced that would be significantly compromised with sucker removal. I don't prune away suckers from stocky, short Dwarf varieties, either, since they stay well in bounds, growth-wise, and it is good to have flowering throughout the season (I consider Dwarfs to be very slowly vertically growing indeterminates).
So there is no right or wrong answer to "should I prune away suckers" - it depends. Suckers don't sap energy from the plant and don't result in smaller fruit. They are just the plant's way of ensuring it produces as much seed as possible- via the tomatoes produced.
Here is a brief video where I demonstrate and discuss tomato pruning.