There are so many deals around at the moment it's hard to find the best. You need to look at whichever package offers the games/accessories you want. The deal at Gamestation for £209.99 was the best one for me...everything I wanted!
And, no technical difference between a white and black one...just the same as what Nintendo did with the DS Lite etc, just made lots of colours but all the same machine. If you go for the black one bear in mind that any extra controllers you may get in the package may be white.