I've had a lot of laptops (I've got three right now), but your question is hard to answer in its present form. The first thing you have to do is figure out your exact list of requirements. Where you have conflicts (need high memory, low price,) sort those out. Then you can start to make decisions.
MACs are nice, and will do everything you need for photos, but if you're planning to do anything EXCEPT photo processing, PCs have much more extensive software. I travel a lot, and I like to keep a Streets & Trips, an Oxford dictionary, a Webster's Dictionary and Thesaurus, and a couple of encyclopedias on my hard drive, as well as some miscellaneous stuff, and it's much easier to get good quality reference programs on PCs. You also don't have compatibility problems with other business computers.
In the PC world, I think the best screens are on the Sony Viaos. Within the Viao world, you can get almost any combination of drives, memory, and ports that you need; prices can get pretty stiff. If you'll take a lesser screen, then there are a million different possibilities. With Dell, you get adequate machines and a realistic price, but the screens are not as good as Sonys.
If you type a lot, the best keyboards IMHO are on IBMs and the screens are good, if not quite Sony. If weight is a consideration, Toshiba has very lightweight machines with OK screens, but much of the weight savings comes from moving stuff like CD burners off-board.
If price is a problem, you can often get great deals on used laptops; especially great if it's a big brand where you can take the drive out, throw it away and essentially start over. Several brands of laptops now offer built-in CF readers, but not Sony (as far as I know.) They were still pushing memory sticks that last time I looked. That's not such a big deal because most computers still offer PCMCIA slots and you can now get high-speed adapters and just permanently keep the adapter in the slot.
I've never found battery life to be much of a problem -- just get another battery. I keep a converter in my car and can charge cell phones, laptops and camera batteries as I drive.
So...the biggest deal is designing your system. After that, there'll be plenty of answers.
JC