If I had a choice on it, I would go for more storage. Now, if you asked me between the 4200rpm and the 7200rpm, I would go for faster. Really, to me anywyas, between the 72 and the 54, there really isnt much of a difference. As for load times, maybe 2-3 second difference? In my experience, my 5400rpm drive, I dont notice the 'wait time', but when I run out of space, oh yeah, I would know and curse myself for it.
As for your question on the following games, Sims games, definatly, with Movies and Half-Life..you may have to 'tweak' the graphics alittle and may get very little lag/choppiness. Remember, its a laptop, not a desktop with the high-end vid card. In either case, you should look for a laptop with its own dedicated video ram, not one that is 'shared'. More dedicated video ram, the better. My opinion, NVidia is better than ATI, but seems to be a toss up now a days.
Hope that this helps, and good luck.
I'm thinking about buying a Dell XPS M140, but I have a few questions. First, is it better to have the 100 GB 5400rpm Hard Drive, or the 60 GB 7200rpm Hard Drive? The extra space would be better, but do the rpms make more of a difference? And also how good is this with gaming/graphics? For every good thing I find about gaming, it seems that I find 4 bad things about it. I won't be playing much, just stuff like The Sims 2, The Movies, and at the most Half-Life 2. Will it support these games?