there are many answers to your question & two other forums on GW could give you better answers ie seed saving & botany...that said ...
1) I have not read any research papers showing coralation between seed size & size of plant etc.....
2) My grandfather was a home gardener from the late 1800's to 1950... He saved seed but it was from plants that had the characterists HE saved seed from plants that produce goo tasting food & those that had high production. & did not look at the size of the seed

Proof? No. It doesn't exist because there are far too many variables in your hypothesis - "larger seeds = better plant and better harvest" - to be able to prove it.

Opinions? Sure. Millions of them. ;) Post it on the Seed Saving forum or the Growing Tomatoes forum as it comes up for discussion both places now and then if you want to get opinions.

IMPO based on many years of growing tomatoes from seed - with the exceptions of very old seeds or very dessicated seeds or seeds that were improperly stored - it makes little or no difference. Instead it is the growing conditions provided, once germinated, that have the greatest impact on plant health and production.

Dave

I can not speak for garden stuff, but as an old wheat farmer. Tests made my selecting larger wheat seed by screening gave a slight improvement in yield. Stronger seedling. I think it was some thing like 5 percent. I am not saying that this would carry over to future generations. I will leave that opinion to the experts.
KennyP