All good points above.

One reason Sidwinders are good is because they were designed from scratch and the machinery was all new to make them. All the new toys and advances in one scope. Priced very keenly too. To get all the features make them a bit big. They shpuld be repeatable for a good while, ie all the parts keep working and doing what expected.
When a manufacturer brings new technology, new machinery, and new models often the products are pretty good. Though its needs to be new design rather than some dusted off old one.

A good few branded scopes are older designs from older machinery with a few bits remodelled just to look a tad different.
Choice of coatings also adds to the mix, cost, and light performance.

Yep, its a minefield, which is why few recommend a scope. Just too many variables.