obviously the quality of the materials, the construction, the quality of the electronics ...

Fender is the best , IMO
Quality, sound, playability, durability. That's pretty much everything.

Few strat copies are good. Every company has copied the strat, but few have done it well.

The only strat copies that could be regarded as being better than actual Fenders are either Tokai, or the ones more expensive than Fenders, like Suhr and Tom Anderson. Whether or not they're worth buying is up to you.