looks like you are not a power user, so a nokia 900 is perfect. usually goes on sale brand new for $200 or lesser. the hardware is rock solid. i've seen people using the phone to drive nails into wood.
The downside of the 900 is that it's Windows Phone 7, not 8. Not that 7 isn't stable and smooth - I'd take it over any pre-Jellybean Android phone - but you'd still want WP8 for a new phone for better updates.
The new Nokia Lumia 925 is 4.5", though, which is still smaller than the Nexus 4 and not substantially bigger than many of the 4.3" phones. Plus the camera in all the new Lumias is very good. I would be happy to have that WP8 smartphone.
4.5" screen for the Lumia 925, device size:
5.08 x 2.78 x 0.33 inches
4.7" screen for the Nexus 4, device size:
5.27 x 2.7 x 0.36 inches
The Lumia 925 is a bit shorter overall than the Nexus 4.
For a 4" phone, I would only really look at the iPhone 5. Very few current Android or Windows Phones I would want in the display size.
The Blackberry Z10 is also an option at 4.2"