Firefox is just bad on all accounts, Dolphin has a tacky UI that feels unfinished, Chrome is only available for less than 2% of Android phones out there. If you don't like whichever browser came with your phone, get Opera Mobile and/or Opera Mini and have done with it. Mobile is better on faster data connections whereas Mini is better for 2G or slower 3G connections, plus the data is compressed before it is sent to your phone, so if you have a limited amount of data on your plan it helps there too. Opera Mini also takes up a lot less space on your phone and will run better on older devices, but if you can afford the space and data and mostly use faster connections, Opera Mobile is a nicer browser to use.
Of course, you could just get both.