basically amd has their memory controllers on-board wich speeds up cache + ram read and writing up considerably wich thus increases cpu speed, pentium M on the other hand has a large on board L2 cache (can be compared to the pentium 4 Extreme Edition). The main reason it saves this much power is because it downclocks according to useage/power left (if on battery).
i'd at least go for the 1.73 Ghz one, or try looking for a laptop with a AMD 64 processor in it. (if possible the soon to be released Venice mobile cores).
a good laptop would be the Amilo A1630 (believe thats the name) has a 3700+ 64 bit mobile in it, only the gfx is the bottleneck in that one. (still beter than those intel integrated gfx chips though