vi_ is right - on top of that, I would say "dual" mode is the most battery-eating. 3G, obviously, show higher usage in tests, but it's hardly noticeable in real life, if You're on area with good coverage.

BTW, it's worth to mention, that even in "high mobile Internet infrastructure" countries, there is generally better 2(.5)G coverage, than 3G, so 3G may suck more battery, just because weaker signal reception.

/Estel