I tried the tomato cages and they just crumble under the weight once the tomatoes start getting big. I ordered tomato ladders from gardeners.com But, I like using two for each plant instead of just one. They really do hold up well. I just planted 8 tomato plants.
I use concrete wire and build a cage that is about 2 foot across. I anchor them down with a tpost to keep the wind from blowing them over. I like them because the lasrge openings make it easy to reach inside to pick tomatoes and not damage them when getting them out. What ever you use I strongly suggest anchoring them in some way or form to keep them from blowing over and injuring your plants.