Originally posted by: Zap
The RAM choice depends on the notebook manufacturer's choice of chipset and implementation. DDR has a hair better latency while DDR has a hair better possible clock speed and lower power usage. Then again, most people wouldn't be able to notice a hair's difference. The cache difference isn't all that because the last gen Pentium M (Banias) used only 1MB cache, so the Dothan Celeron M is as fast as previous Pentium M, even to the same FSB speed. The Dothan Pentium M can be had with either 400MHz or 533MHz FSB speeds depending on speed grade, and some speed grades have both available.
The only difference purely between the CPUs that REALLY matters is Speedstep, meaning Pentium M will average better battery life than Celeron M, all else being equal.
In RL (real life) there are other differences due to marketing and price points. Though the CPUs are close enough, many manufacturers will only put Celeron M in lower end notebooks and Pentium M in higher end notebooks.