I've never had real success with growing tomato plants in 5 gallon buckets, but I didn't have a watering system for them, so that might have a lot to do with it.
There are several types of tomatoes that I grow every year, as well as trying varieties that I haven't grown before. For paste type tomatoes, I like the good ole Roma variety, and I also really like the Amish Paste tomatoes. One of my favorite non paste type tomatoes is the Black Krimm. They get fairly big and are a lower acid type. I usually also try to grow a couple of Brandywine tomato plants. They're an heirloom type that has large and usually misshapen tomatoes that have good flavor. I use them for canning, they have a lot of juice so you really have to boil them down to make sauce if you wanted to use them for that.