I agree with Miles, for even as a first time Mac user I read a lot of misinformation spoken on here as regards configuration.
This purely depends on the use you are putting it to, and I think the majority will be the same as me, internet, watching live TV or streaming from iPlayer etc, listening to music, watching films, and running a selection of programs, but not intensive Photoshop, Autocad and the like.
For this the basic spec is fine, and could barely run anything quicker or more stable, so the likelihood is that you will never see a limitation on your memory or CPU. The proviso is the SSD capacity, 64gb is fine for me but some may need the 128gb if they are going to store a lot more data. I doubt if this would be the case on the move, and I bought a low priced pocket 500mb external drive if I wanted to put a lot of stuff on it.
I think the inclination is to go for the highest spec in the first place as the MBA can not be upgraded, plus advice given by a lot of the posts on here, whereas the standard spec will be fine for the majority. If you can and do not mind spending the extra that is fine, but not necessarily good advice to those asking what THEY should go for.
For me it would have been an extra £360, nearly 50% extra over the cost of
the basic spec, so was just not on. Plus it would have made no difference to my usage.
Everybody has their own opinion of course, just thought that I would keep it balanced.
tut