IMHO, if you're using an Elite 4200, which is rated at 95% light transmission, you're not going to do much better than that. 95% is about as good as it possibly gets, science-wise, for a
variable scope. You could pay another $1000 to $3000, and I seriously doubt you'd be able to tell the difference. Maybe a tad around the edges, but then that's not where the cross-hairs are located, eh?
A 50mm objective might give a couple extra minutes at last light...maybe.
Lots of marketing, everyone of 'em is the brightest with the mostest.
Only so much is physically possible with light transmission through a series of lenses at the end of the day.
Don't fret your Bushnell 4200, they're a helluva good scope.
Spend the extra dough on another rifle and 4200 scope for it!
PS: I've got a Leupold VX-III 4.5x14x40 with "indexed" lenses on my 300 WM Vanguard, and my son-in-law has an Elite 4200 4x16x40 on his Rem. 700 XCR 300 WSM. Frankly, I'd give the edge in overall brightness and clarity to his Elite. Plus, he has Rainguard, which I wish mine had. And his was only a couple hundred bucks cheaper than mine. Only advantage to the Leupy is that it's more compact.
I've read that there are only a relatively small handful of manufacturers of optics lenses worldwide, most of 'em off shore in Japan, China and Europe. And almost all scope makers buy their lenses from these suppliers. Coatings is where the rest of the difference enters in. Japanese makers have an excellent reputation for optics, which is where the Elite scopes are made.