I've got a 350 (I bought another one for replacement) and I've purchased a T1 (that will go to my sister in law), so you see what my opinion is
1.- I have more than 100 books in my 350, and I don't feel the big delay.
2.- I much more prefer 5" than 6" (my 350 always goes with me).
3.- I'm not interested in audio (the audiobooks in my iPhone die a slow death).
4.- Wifi is not a must for me (no book goes unprocessed to my ereader and I don't have all my library in calibre or dropbox).
5.- I feel much nice the feeling of the 350 library and features with PRS+ than T1 without it (non fair but this is a real word)
6.- Android isn't a selling point for me. I can't care less about the OS my reader has (I'm always has been a high-level software girl
)
But, in the end, go with you feel more comfortable, I think you'll enjoy it.
BTW, I think I prefer Kobo Touch (yes, I already have it
) than T1, and that for sure if Kobo implements collections at some moment.