I grew Rio Grande about 6 or 7 years ago. It performed well enough (though not as well as I had expected) that I think I grew it for 2 or 3 years but it does not compare to Heidi. Nothing matches Heidi in our typical hot, dry weather. If I could grow only one paste type, it would be Heidi.

Rio Grande was one of the primary candidates I trialed, when investigating about a replacement for Roma VF in my regular line up. You can see a bit on that in a thread over on Green Country Seed Savers:

What varieties do you grow? (Rio Grande is third post)

I found the plants to be size of a Roma VF plant and the tomatoes are larger. They are of excellent quality and keep quite well. I really should have trialed Rio Grande for one more year. But, as Dawn mentioned, Heidi blew it away in my trials. I'd say that Rio Grande has somewhat higher quality fruit. But Heidi's fruit is really quite good. Hey! It's January 7, and I still have usable Heidi tomatoes on my kitchen counter!

Here's picture of Rio Grande.

I was wondering about Rio Grande because they are supposed to be large type.

Several years ago I had two tomato plants volunteer in my garden. I moved them to a row and let they grow without staking them, they sprawled all over. The two plants produced 76 Roma type tomatoes and still had a few when it frost that fall. The original tomato came from the grocery store so I have no idea what they could have been other than Roma but I was truly impressed by how many they produced. Some times even a blind hog can find an acorn.