I had my Lumia 720 for 1,5 year and I replaced it with a Lumia 735 about one month ago as I got some extra cash to spend. I am still using my 720 for testing purposes, having installed Windows Phone 10 and my frequently used apps. My first impressions from 735 so far, compared to my long experience with 720, are the following:
Screen: Lumia 735 has slightly larger screen and higher resolution. Both are more than welcome and nice improvements over 720.
Battery life: I still have the impression that Lumia 720 does better in terms of battery life, even though tests and specs are against that. Maybe it is the specific unit or my type of usage, but I believe that 735 drains battery faster using the same settings e.g. for brightness, battery saving and apps allowed to run in the background.
Camera: Mixed feelings here; Main camera has the same sensor and lens and the images produced may be a little sharper and with ore vibrant colors. In addition, front camera is a big improvement at 5MP. However, the lack of a physical button for the camera is a main issue, at least to me; it is really hard to take a selfie trying to reach and press the software button and even for normal photos, it is always easier when having a dedicated hardware shutter button.
Other features: Both phones support NFC out of the box; Lumia 735 also supports wireless charging (charging pad should be purchased individually) as well as 4G (compared to the 4G of 720); both are nice improvements. 735 does not boast a unibody design, which means that It supports interchangeable covers and user replaceable batteries. So far I have not noticed any cranking noises, which was really nice.
Overall usage: Both mobile phones are really snappy in terms of everyday use. What I like in 735 is the fact that it features the hidden menu bar which bears the typical Windows Phone buttons (Back, Home and Find) – this allows for a little bit more usable space for typical usage and it just comes up by sliding from the bottom to the center of the screen. It took me some time to get used to it but now I love it! I also like the organization of the settings in groups; both improvements must be due to different software versions between 735 and 720. Another nice improvement are the hardware buttons which feel more responsive compared to the ones of 720.
Conclusions: I like my brand new phone, its larger screen with higher resolution, its bright-green colour and new software features. At the same time, I am still really annoyed by the lack of a physical button for the camera as it seems a major usability issue to me – but maybe this will make me use my Olympus E-PM1 mirrorless camera a little bit more!