which apple laptop ?

If you're doing high end photography stuff I'd recommend a 15" MBP. The MacBooks are pretty much on par with the MBPs in 2D and photoshop work. The only issues is that Adobe is increasingly using GPU calls to run certain filters in photoshop. Also, ATI/AMD and nVidia are both pushing to use the GPU as a multipurpose processor when it has spare resources available for the system to use. As these features are pushed on the hardware end, companies like Adobe will push back on the software end to nudge the hardware engineers forward.

In any case, with the 15" LED backlighting that'd be the best option for photo work, per the wider color gamut. You can make do handily on a MB for most of your needs. Also, doing photo work, you'll be better served by using a larger external monitor for those "nose against the monitor" moments of graphics work. So, in that instance you may opt to get a cheaper MB to accommodate the expenses of an external monitor, assuming you won't be doing anything too crazy in the way of say, a 200MB+ image file.

Others may have experiences to the contrary, making the MB a solid option even for high end work. Personally, if I did that work regularly I'd easily opt for a MBP over a MB. As it is, I only get into big photoshop projects every now and again, so the MB works perfectly for me.

AFAIK the only thing Photoshop uses the GPU for now is for PS CS3 Extended which allows you to bring 3D models into the programme. All of the filters are still done through the CPU.

For what you are doing, the only things that you may want from the MacBook Pro would be the larger screen that yields a higher res, as well as the ability to drive a larger external display (1920*1200 max res MacBook, 2560*1600 max res MacBook Pro)

As far as processing power goes, they are basically equal, and can hold the same amount of RAM, so really... get the MacBook, and then spend the extra cash on 4GB RAM (not from Apple) and a 24" Widescreen Dell Monitor (2407FPW-HC)

I have, works wonderfully. :-) I got 2 individual sticks of the same model from Newegg for $80 after rebate ($60 after a paypal promotion) and they have been working flawlessly. :-)