What makes Opera Mini is very popular on the Android (which also has a browser built-in) is a reduction in the amount of data traffic - because with Opera Mini can save data and faster even in the 2G network coverage only. That feature, Opera Turbo, is also part of the latest browser Opera Mobile 1.10 beta is more or less can save up to 80% of data traffic.
Mobile web browser Opera has got something that Opera Mini does not have the pinch zooming. Features such as Opera Link and Opera Speed Dial is available as well and not miss the featured download manager, password manager geographic location and SVG support. 10.01 Opera Mobile beta UI looks very similar to the mini UI, which will make the transition from Mini to Mobile easier. See the video to see Opera Mobile in action.