it’s a bit weird right now. The thinnest lightest one isn’t the Air, it’s the ‘vanilla’ MacBook. Which has retina, but you need to be aware that it has naff-all ports so to plug anything into it requires relatively expensive dongles and looks a bit silly. Really depends a lot on how you’ll use it.
The Air seems semi-abandoned at the moment, the spec is quite low, no retina. Don’t really see much point in them right now as a new purchase.
The Pro is …different depending on if you’re looking at 15″ or 13″ so it’s not straightforward to summarise. But it’s not bulky or anything, anyway. I just upgraded from a top-end-at-the-time five-year-old one to the current top-end 15″ and it’s v. nice. Work are paying though so it’s easy for me to say.
If you really are just using the web and nothing else then the Macbook will probably suit you well. Then again so might an iPad.
The Air is available in a retina model.
no it isn’t. it’s not a bad screen or anything, but it’s not retina. Here’s some more geeky theory on its probable extinction