Feifer,
Good question. You could certainly do that and be happy. I just don't use my high range variables much on the highest power, matter of fact the Burris and Leupolds in the range you are talking are not currently on rifles. Only exception is a 5.5-22 NXS and it is on a 17 pound bench rifle and it is a sharp, bright scope at 22X but more $.
The lower range variables are smaller and lighter and really effective on my .223's. Guess this comes down to personal preference - if you really want a higher power range scope in 30mm with side paralax and 50mm objective then go for it. Sometimes we got to scratch an itch to feel good, right!
To better answer your question, I find that the image is brighter and seems sharper when I crank the big scopes down to midrange. That is usually 12-14 or so. Eye relief is definitely less critical. When I put the 14, 15, 16 power scopes on max they are sharp and bright -- just works that way for my eyes.
Just to muddy the water a bit more, I really doubt that the 50mm objective will give you much over the 40's in most light we shoot varmints and targets in.
Going to a 50 means higher rings and that can pose some headaches re stockfit and even scope-barrel clearance. I was told by someone I trust that one of the primary advantages of bigger lenses is that they can be ground with more precision so the image should be superior. Brightness is not near the factor that we expect since the light has to "squeeze" through a very small tube inside the scope before it gets to our eyeball.
Buying a scope is a big decision since we have expectations that we hope to meet. It is tough when you cannot directly compare models, some stores stock enough that we can hold X up to our eye for a few minutes and then try Y, but that is not a realistic way to access optics. We can get good input from experienced shooters but we must be aware of brand allegiance biases (no idea how to spell that word).
I happen to look at scopes from a somewhat different viewpoint today than I did several years ago. Optical qualities are important but I now put much more value on quality turrets than I used to since we use them so much in the LR shooting.
Good luck with your decision, this is what makes our sport fun. Best wishes for the holday season.
