For games on a Intel Mac your best bet is to use Bootcamp so you can dual boot it into Windows XP. Using Rosetta or anything else for that matter will hurt performance. If you do stretch for a MacBook Pro make sure to clock the GPU up to the ATI specifications, Apple down clock them for better battery and heat.(You’ll need to use the Catalyst drivers as the the drivers that come with Bootcamp wont allow you to use any overclocking software.)
From the benchmarks I’ve seen Core 2 Duo and Core Duo are pretty close were gaming is involved, it’ll be processor hungry tasks like encoding video that really sees the Core 2 architecture take flight. If you’re really not in a rush wait until the next iteration of Core 2 Duo it’s expected the early part of 2007… sorry can’t remember the name. Early gossip has it beating the current gen by a long margin. If you’re in a rush though Core Duo is a perfectly fine processor range.
What exactly are you looking for the laptop for? If its for college/work remember a 15″/17″ packed to the gills might sound good but your wallet and your back won’t be too thankful.
Oh just for the heads up Sony produced the Dell laptops which explode…since Sony were mentioned though that should be fixed now.