If you'll be sharing the load with one other person, then you can each carry part of the tent and the higher weight of the Shangri-La won't be as big a deal. For an all-around tent, the Shangri-La seems like a pretty good deal. I looked at the 1 person version for the same reasons as you before I decided I'd just rather get a spring/summer/fall tent that weighed less and buy a separate winter tent when the time comes. You really only need a 4-Season tent if you expect to face heavy snow-loads. It's not the cold that is an issue, it's the tent being able not to collapse when you get 10 inches of snow while you're sleeping.
In the end, it comes down to your budget, and how much you think you'll get into backpacking. If you're going to be doing a lot of backpacking, you might want to consider getting a lighter weight 3-season shelter for this trip, and then getting something like the Shangri-La 2 for your winter camping. Specialization costs money. But your tent is one of your Big 3 (along with sleeping bag and backpack). They cost the most money, and they weigh the most. They'll be the first place you look to cut weight, so it's best to get the lightest of each that fits your needs/budget right off the bat.
You might follow Brads suggestion and look at the Shangri-La 3 though. For the extra weight, the added space could be the difference between you and your partner killing each other over the course of 6 months sharing a tent.