I'm looking for opinions on the optical differences between the Gen-1 and the newer, lower cost, Vortex scopes.
Primarily the 6-24 range.
Glass comparisons and eye box relief.
How does the Gen 1 Viper compare to the newer lower cost Vortex scopes (Diamondback, Venom,and Strike Eagle).

I plan to replace an old 6-20 rifle scope on a Savage striker .22LR pistol that I updated with a 15" barrel and a Dewey target trigger. The eye box is critical.
Most shooting will be 50 yards to 200 yards.

I don't know much about the Diamondback, Venom, and Strike Eagle lines.

Within the Viper line, the Gen 2 is a definite step up from Gen 1 in glass quality. I would not consider buying a Gen 1 Viper. I have a Gen 2 Viper in 2-10x that's a good scope. Other people on this site own the higher power Gen 2 models -- IIRC they all have stated the glass quality is good.

I have several Gen 1 Viper PSTs in 1-4x, 2.5-10x, and a 6-24x and I love 'em. All except the 1-4x scopes are first focal. I have one Gen 2 Viper PST in 2.5-10, that thing is awesome, though the zero-stop is confusing to set.

I also have two Diamondback Tactical 4-14x in first focal. The Diamondback is good for the price, fair value overall, and good for what I needed (a mid-priced scope I could throw on rifles when testing), but not as good as the Vipers. Seems like there is more parallax in the eyebox, glass isn't quite as good, stuff like that.

I cannot comment on their newest high magnification offerings, no experience with them.

How is the eye box and eye relief between the Gen 1 Viper and the Diamondback?

fritz is correct. Common wisdom is that Gen 2 is definitely superior to Gen 1 in the Viper. Having said that, I have a Gen 1 on an AR10 that I've been happy with. Never really noticed eye box being a problem and glass is decent, but not spectacular.

Most of my shooting is 0-200 yards, with occasional sessions out to 500. For that the scope is fine. If you're primarily shooting 200 yards and in, it should work.

But if you end up buying a Gen 1 as NOS, it should be at a spectacular price. I think I picked mine up for about 50% of what a Gen 2 would cost.

I just picked up a 6-24x50 Diamondback for my .308AR as a Blem for a decent price.
Blem meant bent so I got to test out the Vortex warranty.
Just over a week from my e-mail and I had a new one at my door.
They do not mess around, that's for sure.

The only other scopes I have to compare it to are some Primary Arms LPVO scopes.
The eye relief seems good, the end is by the charging handle and I'm not a nose to CH shooter.
With this scope the eye box is much better, using a 1.5" mount I can wear my bi-focals without having to jack my head into weird positions. With the LPVO I had to wear my old pair of readers with a 1.5" mount, I wound up with a 1.9" mount in the end with that setup.

Still have to zero it and try it out but it seems to be a decent 500 yd scope.
With a forecast of 107 deg this weekend it looks that's going to be on hold again.

After countless hours of research on this I have stepped back from the ledge and decided to look into other options.
I own several Vortex scopes but can't say I have used any of them hard.I find them OK.
What I constantly hear is how good there warranty is and how quick and easy they repair or replace a scope. While this is a good thing its also a bad thing in my eyes. I DON'T want to have to zero in a scope only to have to remove it so it can be repaired.
I will investigate other brands.

I settled on a Athlon Argos BTR Gen 2 6x24x50 scope.I was able to buy it for a very good price with a professional discount.
It should work fine on my .22LR handgun.