Unless phone screens go edge to edge i cannot see how onscreen buttons could ever be better? They literally just take up space that could be used for more screen realestate :/
If the bezel is there, then put the buttons on it.
- can change orientation with the phone
- google could decide to do something really cool with them in the future like maybe allow you to add additional buttons, change colours, size/icons and add some additional stuff i.e. could use it to display more info. on a new email or something.......
- the way it changes depending on what you are doing i.e. if you have the keyboard the "return/back" key will change to an arrow pointing down instead i.e. it shows that the keyboard will "minimise"
- one less thing that could break
- the front of the phone looks very sleek/modern/futuristic when the screen is turned of
Essentially more "flexibility" with on screen buttons.
You can currently do most of the above stuff above if you root etc.
But I see your point as well and can why people would prefer capacitive buttons instead.
The thing I don't get though is that all the sites and even google said themselves that having on screen buttons would reduce the bezel, yet it just makes it worse :/
Personally I love the thought of having very little bezel all the way round, however, how practical would this really be when operating the phone with one hand? Currently with my S, I sometimes accidentally touch the screen due to how thin the side bezels are and imagine it would be much worse if the bottom bezel was the same size.