I don't think a Macbook Air will make a primary recording machine is you're planning on running anything besides maybe a dozen audio tracks. I have a Late-2012 Macbook Pro, and it gets pretty sad when it has to process a lot of VST instruments (roughly 6 before I have to freeze tracks) although I haven't seen it reach it's audio track limit though (I've gone 24 tracks at most though)
So if this is having some issues I can't imagine a MBA being a good choice
And that's not even factoring in storage and screen size if you're planning towards an 11"
Actually, if you could push the RAM up to 8Gb it might even work.
Not saying it's the best option on the market but if you're not going to use 10 or more VSTs, it does the job.
Probably not gonna be a good choice. I've got an early-2011 MBP w/ a quad-core i7 and 16GB of ram and it's only ok with Pro Tools. I do sound design and have a lot of plugins running at once and it gets noticeably bogged down. If I have a video track in the session, forget it.
If you don't need to be portable, I'd suggest looking at a 2nd hand mac pro from a couple years ago. It'll have way more connectivity and power.
Unless you NEED a laptop you're better off with an iMac (I have one) or MacMini with a bunch of external drives.
ANY daw (mac, pc, whatever) you want:
Lots of RAM (8 or 16gb, it's too cheap now to bother with anything less)
Fastest processor you can afford (i5 good, i7 better)
Several drives*
*Best setup for any daw:
OS, apps and plugins on boot drive
Sample libraries on a second independent drive
Audio projects and misc data on a third independent drive