Depends on your needs.
If you absolutely need a maxed out MBA or rMBP, then go for it. On the other hand, those are extremely underpowered computers for the performance benefit of maxing them out. If you do not already have a top of the line desktop from the last 3 years, I can almost guarantee that you do not need a maxed out 13" laptop.
My recommendation is based upon the assumption that you have a top of the line desktop. Get a MBA if you need a portable, all day solution. Get a rMBP if you are doing heavy photography work while you travel. The main benefit of the rMBP over the MBA is the screen and performance, but if you already have a desktop, the overall performance gap is not noticeable. I don't know what your usage is, so you have to make the final decision.
TL;DR: Do you have a really nice desktop? If not, buy one before you buy a maxed out 13" laptop. If you do have one, get a MBA for all day usage and get a rMBP for more accurate editing capabilities on the go.
Matt
