To be honest they are all much the same. You could get a Centrino that doesn’t require a PCMCIA card, this is beneficial as its safer to be carting around, as there isn’t any bits sticking out that can be damaged.
That said you can always take the card out and store it, personally I find all WIFI cards very similar, you can get extended aerials and plug inns but to just log in to a hotspot to jump the net all seem to suffice.
If you are out and about a lot, battery power is a major concern. Are you going to be using the machine with power hungry apps? Tech on mobile computing has moved forward a hell of a lot but bat power isn’t moving at the same speed. click here and have a look at a few, it’s a good site that offers lots of options.