There are no 'range specifications'. There are so many variables that affect range that there is no way to standardize. Radio used, antennas used, environment, interfering RF, obsticals...and a bunch of other things affect the RF.
Any wifi engineer will tell you all the specs and numbers in the world can only give you a vague idea if it will work or not. Experience will give you a better idea. But actually installing and trying it out is the only way to know for sure.
What is best is determined by your environment. A lot of obstacles - walls, trees, cars, etc? B/G will be better because they are lower frequencies and will propagate through material better. Not good, just better than A.
Is your area saturated with wifi nodes, cordless phones, microwaves, etc.? A will be better because it is a different frequency band than all these and the spectrum is usually not as crowded in that range. Less interference = better reception = longer range.
Josh
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