I have a couple 3-15 G2B's, a 4-20 SCR and a 5-25 SCR. I also have a Steiner P4XI 4-16.
The Steiner P4XI is my favorite of the bunch with the best glass clarity, but a little CA.
One of the 3-15 XTR2's has spectacular glass, and the other is poor, but not bad enough to warrant sending it back.
All of the scopes seem to track great. I have had the Steiner to 800+, the 4-20 and the good 3-15 out to 1000 with great results. They seemed to match perfectly with the ballistics app, and no I haven't done a tall target test.
The CA is really bad on the 5-25 and clarity is not too good over 20. I only paid $630 for it at optics planet, so I feel it is still pretty good for that price, but I might feel different if I had paid $1000.
The 4-20 is just a really nice scope. Not bad CA, decent glass, and those fantastic turrets. Way worth the money.
In the future my money is on the Steiner P4xi as long as I can still find one.