I picked the regular City Mini over the GT. My husband loved the GT because it felt more sturdy and better for rugged terrain, but I reminded him that I'd be using it at WDW, at the mall, and when we were really roughing it, on sidewalk paths at parks. The regular City Mini is fine for that, plus it's lighter. You'll appreciate it being a few pounds less when you're lifting it into the back of your car with your baby on your hip, and it's particularly nice when putting it on a tram in a WDW parking lot. I think I could handle a GT if I had to for our single stroller, but our double is also a City Mini, and I would be very discouraged if it were a GT.
It really depends how you're going to use it. The benefits of the GT may just end up being more of a hassle if you don't really need the GT.