The differences are narrowing considerably. Moreover, the plain fact is, all the development money is in consoles right now, so that is where virtually all of the development is.
And this trend is only going to get worse I think. The console dev money is huge. If you are a seasoned developer with great tech and Triple A talent - consoles are your main focus these days. That's the way it is and it is only going to get worse. (The reason is simple: it's all about piracy).
Triple A pc titles are exceedingly rare these days. The big genres for PC remain MMOs, Strategy (which, due to interface issues and limited memory, consoles don't do very well) and shooters.
(And I expect the MMO scene is about to come alive on the 360 and PS3 as well in the next few years).
RPGs and action titles have moved pretty much to the console platform. The exceptions are high value moddable RPGs like NWN2 and Dragon Age games which are still king on the PC (and about which I know a little something

) Oblivion, ostensibly a cross platform title, plays much better on the PC but it does play on a 360.
I prefer shooters on the PC - but that does not mean there are not great shooters for the 360 and (someday) the PS3. Gears of War, while not strictly an FPS - is a shooter hybrid and is state of the art. Only on the 360. The forthcoming Halo 3 - ditto
If you were asking about gaming on a desktop or reducing your video card and getting a console...I might hum and hah and persuade you to stick with PC.
But if your choice is a laptop with *marginally capable and mondo expensive* hardware and no console - vs a serviceable laptop and a next gen console - the answer is simple: get the standard laptop and a 360.
Is your choice is a Mac....well that is no choice at all. Get a 360!! The games available for the Mac are few and far between.
I have a few laptops, 2 gaming desktop PCs, a PS2, Xbox, a 360 and a Wii. I do not (yet) have a PS3 and the only reason I would get one is that a project I might work on would require it. There is no way you can be into games in a serious way these days and not have a console though. That's just the way it is.
For adult targeted games, the 360 is the best current choice. The Wii is a great little system though, and it's hella fun. IF you can swing it - get both

The PS3 costs as much as a Wii and a 360 put together!
I would not invest in a gaming laptop of any kind. The hardware is sucky, over priced and the game experience it delivers on anything but the most ridiculously expensive Alienware rigs are substandard. And you can't upgrade them (note: Asus demonstrated an external PCIE video card rig for laptops at CES last month that allowed upgrades. But that tech is not on the market yet and there is no word on price).
Short strokes: save your money and get a 360.