Best 7mm? Best at what?
Not the fastest, but my favorite, is the old 7mm Mauser (7x57). Next would be the 280Remington.
If you like small bore magnums, the 7mmRemington Mag. is hard to beat.
I don't much care for the 7mm-08 or the 7-30Waters, nor the 284Win.
No use whatever for the WSM's, RUM's, or SAUM's - just a lot of hype to sell more rifles.