I disagree that both have good browsers. What I'm worried about is the lack of emphasis that seems to be placed; Android browser is missing a lot of html5 features (according to caniuse.com it only supports 66% of current features in Android 4.0).
Mozilla, on the other hand, seems to be making mobile a priority with all of the work they are doing in WebAPI. Their browser is updating a lot faster than Android's, which I believe still only updates with OS upgrades.
