6.5 Grendel is definitely one of those chamberings that sees significant performance difference based on what optic you put on it.
You almost can’t put enough scope performance on it, but you can put too much scope size/weight/bulk if you’re going for a more handy, lightweight set-up.
With 5.56, I feel like most of the modern modern LPVOs are overkill for the limited cartridge performance. You can slap larger magnification on an SPR-type set-up, but you’re just splitting hairs on how well you can shoot within its anemic limits on-steel.
With Grendel, you just see more and more hit probability in your favor at distance, where for most people, it’s hard to find ranges that support 800-1200yd steel TGT opportunities.
That’s all talking target. For hunting, a lot of people want either a simple hunting scope, or a dual-use TGT/hunting scope. That’s where we get into which turrets you want capped, weight, bulk, etc. Those Vortex Viper PSTs and HSTs would be great for that, if you could get capped windage and locking elevation.
I would be shooting the Burris 1.5-6x42 all the time if it had a good tree reticle in it. It’s really light, great FOV, clear, solid little scope, handicapped by the reticle they put in it. Would be fine on a 5.56 though.