Re: best full length sizing die 7mm-08
I've been reloading for a very long time. Used and own a large number of sizing dies from more than a dozen makers and have found NO average effective difference in the effect of a sizer by brand. As you note, they all do the same thing so brand is no quarantee of anything but price and external appearance.
You are correct that all brands of die's inside dimensions are normally cut to SAAMI specifications. That's a range of a very few thousants and anything within the range is fully as 'in spec' as any other, meaning there no specific dimensions they aim for. All die makers use SAAMI spec FL die reamers so there is as much average variation between size dies made by the same maker as there is between makers. (And there's less difference in the end effect of most seaters by brand than many seem to think.)
A small base die is usually only 2 or 3 thou smaller in the base area. In a metal to metal fit that much can be important but for bolt rifles it's rarely helpful and it's not needed nearly so often as is commonly assumed for autoloaders.
Many of us like Lee's collet neck die better than any others because of it's design principal. We usually get the straightest possible sized necks of the proper inside diameter to obtain the least bullet run-out possible with our cases and methods and we don't have to fiddle with assorted bushings to get it. But no neck die alone is going to do the job; you WILL need either and FL die OR a body die to use with the neck die.
This isn't as satisfying as swearing that a specific brand and type is better than all others but it's true; pick something that looks good and try it, it will likely do very well. Bottom line, what we get with any brand of conventional dies, perhaps especially for FL sizers, is mostly luck of the draw.