For me the shatterproof screen and expandable memory were the two big draws to upgrade from the T1. Otherwise, they seem to be comparable in most aspects. The battery may be a bit worse, but my phones sit on a charging cradle overnight and on my desk at work most of the day. I very rarely see it drop below 80%. I was concerned when I read reviews that stated that the materials used to make the display shatterproof resulted in a dimmer or "Dingier" image. I have not found this to be the case at all. I find the display bright and crisp. Holding various phones side by side with the T2, I would say the display is just as nice as any phone out there. Sure, the latest galaxy phones, the V10, and possibly the iPhone 6plus may have a little edge here, but by no means is it a blow out.
If you are basing it strictly on user experience, I'd say stay with the T1. Your day to day experience will most likely be exactly the same. If the peace of mind of having an almost indestructible screen and the added benefit of expandable memory are worth the expense, go ahead and upgrade.
Tony