So, today I did a taste test - three batches of sauce:
1. Imported Italian (not San Marzano) whole tomatoes w/out salt, calcium chloride or citric acid
2. Canned tomatoes - diced w/citric acid and calcium chloride (would have been better if they had been whole, but that's what I could find - Trader Joes brand).
3. Pomi strained tomatoes - pure tomato, w/out salt, calcium chloride or citric acid
And lo and behold, the imported tomatoes w/out citric acid, calcium chloride or salt were the winner! The sauce was sweet and fresh tasting. Even opening the can, the tomatoes were brightly colored. The Trader Joes tomatoes were not a bright red when I opened the can. And the sauce with the Trader Joes tomatoes was quite acidic - I feel the need to add sugar to it. Additionally, they did not break down (just like you said!). The Pomi tomatoes were alright - but made a much thicker sauce. I do think they would be perfect for a pizza sauce though!
I realize my test was not perfect, but I still learned a lot. I just wanted to say thanks! I always wondered why I needed to add sugar to my sauce. Now I know! Such a simple solution. I'm just amazed at the difference.