Which Mac laptop I should buy?

I am currently using the 13" Macbook (Late-2009, white unibody) and am looking at the 13" Macbook Air. I am a software developer and have a work laptop that I do my actual development on. However, I like to dabble and learn new programming languages and frameworks in my free time. It's been awhile since I paid attention to processor power and hardware specs, so I am just trying to gauge whether the 13" Macbook Air will be enough for me. I'm drawn to the Air because of it's slim profile and light weight.

I occasionally run linux VMs using VirtualBox, and do not plan on running any windows 8 or 10 VMs.

I would be upgrading the RAM to 8GB, and am trying to determine if i should upgrade the processor from the 1.6GHz i5 to the 2.2GHz i7. Can anyone provide some suggestions?