Actually, here in the US, the price difference is less now.
The best price I've seen for the 735 is $300.00 from B&H and I'm seeing the 830 around $370.00 now.
Again, not d'ssing the 735, it's a great phone, just saying that the 830 has more features and a more premium build quality.
If the screen were a little larger on the 735, I may have kept mine.
Spec wise (4.7 vs 5.0) it doesn't look too much smaller, however, for me, in real use it was because the nav. buttons are part of the screen and on the 830 they are not. Granted the nav buttons can be slide out of the way, but when typing they do take up sceen space which they do not on the 830. That was rather important to me.

Fred