I have both 350 w/ PRS+ and T1 (not rooted). Both are great for different reasons.
Why I love the 350:
* The screen is a tad sharper than the T1. (But the T1 is still very readable.)
* It's small and portable.
* When you add PRS+, the 350 has the best customizing options of any reader I can imagine (better than the T1).
Why I love the T1:
* The screen is larger so you can see more of the page at one time. (Though the 350 is still comfortable to read.)
* WiFi! No, it's not a necessity, but it's soooooo nice to be able to download books wirelessly rather than having to tether to a computer.
* Landscape orientation works perfectly. (In the 350 you get repeated lines on the screen. ADDED: This feature will be coming to PRS+ soon. Yippee!)
* ADDED: Menu navigation is more efficient (for the way my brain works; other brains may conclude differently).
If I had to give one up, I'd let go of the 350 and keep the T1, but honestly, I don't think you can go wrong with either choice. It's just a matter of which features you value most.