How can I tell the difference between Tomato plants?

smell em... if they smell lik sweet, girls, boys, or beef

In my experience, I believe you will have to wait to be sure. These are all regular leaf varieties. You might be able to make some guesses based on what you know about the varieties. For instance, the most mature-looking plants now might be the earliest variety to mature, which I assume would be Early Girl. Romas tend to have a stocky looking plant, but I'm not sure you could tell that much from a 10-week old plant. I had a similar problem earlier, when my 2-yr-old granddaughter took all my labels out of one seedling flat!

What I did was group the seedlings by the similarity of the leaves and thickness of the stalk, and planted them accordingly, but I still don't know which group was which variety. I'm waiting for fruit to know with any certainty.

That is a very good question. I did the same thing you did. I should have labelled every plant but I didn't. I am just watching the growth pattern and watching to see if the leaves are a different shape.

I have been trying to google the name of the tomato plant to see if there is a photo on the web that I can compare the shape of the leaves to.

I'm glad to hear I am not the only one who does this...LOL.

rather in undemanding words from the dimensions of the fruit - for sure cherry tomatoes are smaller. in certain circumstances the plant itself would properly be slightly smaller, too, although the leaves look an same as a time-honored tomato plant