Upgrade to higher memory or faster processor on MacBook Air

Solution 1:

With all that stuff you're running, you probably won't be happy with 4 GB of RAM. If it's truly an either/or decision, up the RAM unless you know that you won't be paging with only 4 GB.

The processor goes from a 1.8 GHz Core i5 to a 2.0 GHz Core i7. I'm not sure that's all that much of a noticeable increase.

As for temperature, Apple will put in a sufficiency of cooling regardless of the processor you choose. I don't really get why people get freaky about laptop heat output: any heat problem I've ever heard of is due to environmental factors that the user (not the manufacturer) has control over.

All that said, I got a 2012 MacBook Air with 8 GB RAM and the 2.0 GHz Core i7, and I'm super happy with it. It's noticeably faster than my previous, a 2011 Air with 4 GB RAM and the 1.8 GHz Core i7, but I suspect that's mostly the RAM and the better graphics between the 2011 and 2012 models.

tl;dr: probably the RAM, maybe the processor. It all depends on how you're going to use the machine.

Solution 2:

The following are some stats of my MacBook Pro (4GB RAM, 2.3 GHz i5) right now. I'm using it for similar things you plan to use your Air for. I have a VM with Windows XP open, some Terminal windows, iTunes playing, Xcode, X11 running, and some Finder windows.

The CPU is more or less idle:

But check the RAM (yes, I have two 8GB sticks coming for an upgrade to 16GB :P):

I think that you can see quite clearly where's the bottleneck.

You should definitely upgrade your RAM.