I have owned both a g7 and a leica 1600 and I prefer the g7. It took me over a year to bite the bullet and buy one, but after shooting side by side with the leica and my shooting partners g7 I finally decided that the g7 was the best option for me. I had a terrapin in my hands as well and although there is no doubt it was the stronger rangefinder. The added options of the g7 made it my choice.
You will have no issues out to 1000 yards or further if you take the time to learn how to use the rangefinder effectively. Understanding and using the different settings makes a huge difference in performance.
We have used the g7 out past 2000 yards with excellent results and I have ranged elk and deer beyond the 1400 yard max of the ballistic program with no issue. You just need to be sure of your target and practice to know your getting a true range.
That being said if you are going to be shooting elr distances 1200-3000 yards than the terrapin would be my pick..but if your primarily hunting at distances under that the g7 is pretty damned hard to beat especially if you practice with the unit.