1. Do you have a budget? The mention of 'Apple' and 'Performance' in the same breathe should include the thought 'molest your wallet'.
2. I really don't like Dell's workmanship. Their keyboards and touchpads in particular turn me off, and Apple is definitely a win here, but I'd cross-shop HP. Consider your discount of course, it might be worth it to just get a keyboard and mouse. You can get a keyboard with a USB hub, wireless units, or a docking station depending on what you're looking for to alleviate a Dell's input woes.
SCII isn't the most demanding game, and shouldn't be considering Blizzard's wide audience. You might also want to tell us what you mean by 'play,' as well, because even the integrated graphics on a 965G chipset used with the first Core processors was able to 'play' World of Warcraft/Lord of the Rings Online/Torchlight. I'd recommend discrete AMD 58XX or Nvidia GTX-200 or 400 series cards for your top end, but these will cost you.
Looking at the basic Macbook, the $999 one, it seems that its Geforce 320M
doesn't do to terribly bad; 48 Nvidia shaders at 450MHz is pretty good for integrated graphics, and it has all of the decoding goodies built in. It can handle WoW handily at medium settings. Looks good if you want a Mac, just remember that it only comes with 2GB of RAM, so you'll need to hit up the Egg.
Looking at the Dells, there seem to be quite a few options. I like the Studio 17
, whose Mobility Radeon 4650 looks pretty competitive- 320 AMD shaders at 500Mhz.
And after some research, I have more refinement questions: what about screen size, quality, and resolution? There's an Alienware that has a low resolution 11" screen that doesn't otherwise look bad, and the Studio above is 17". It's a big difference. Also, the larger laptops usually include a keyboard that has a number pad attached, a relic reintroduced to the masses with the advent of 'wide' screens on laptops. It's definitely something I want in a laptop (1080p screens are usually large, and therefore wide, enough to support them).