as the above poster mentioned those are the differences in specs.
im going to give this a shot but im pretty new to this whole thing so someone correct me if im totally wrong:
practically speaking, i believe that the triple gives you more headroom but it also requires a higher volume to get that sweet tone that mesa boogies are known for. additionally, don't let the extra 50 watts of a triple fool you in terms of how loud it is. the extra power delivered only gives a couple additional dB. of course one additional dB increases the sound tenfold.
The formula for sound intensity is P/A where P=power and A=area.