Well, if you can't see a difference in your negs under normal conditions, just keep the one that feels nicer to use. Or sell the one that can fetch you more money.
Pictures are all that matter, and if if you cannot find any differences in your own negs, why base your decision in lab produced tests or other people's opinions?

I'd even say that you don't need to look hard, using extreme enlargements etc., to try and find the "best" of your lenses. If you cannot tell which neg is by which lens on first glance, it's not worth it sweating over it too much.