Thanks for the replies. In the end I bought the 630. And I am glad I did.
The performance is much better, I have hardly any resuming time. The difference in speed is quite noticeable. Eg with Skype, which I need for my work. Price was only 129 euro.
Battery seems to be doing well too.
I hardly ever used glance, double-tap-to-wake, the flash and front facing camera on my 720.
Edit: I will return the phone tomorrow. Battery doesn't last long enough and I want a better display.