Why get a Mac at all if you're going to be running Visual Studio? Running Windows in a VM and then a chunky piece of software under that is not exactly the most ideal runtime environment.

I'd get the Thinkpad T440 with the 9 cell battery. It will cost you roughly the same as a MBA and less than a MBP.

The Thinkpad T440 is 4.0 lbs, 1 lbs heavier than a 13" MBA and between the 13" and 15" MBP in terms of weight (as you'd expect from a 14" machine).

I will say that the Thinkpad's touchpad isn't as good as the one found on Apple's machines (but those are industry leading). The display is also worse (although Windows doesn't take very good advantage of the "Retina" display anyway). However you gain more port options, battery options, you can upgrade it, it is cheaper, and less "showy" (so less likely to get robbed, etc).

If you REALLY want to get a Mac I'd definitely get the Pro just to somewhat counteract the VM performance loss.

Definitely agree with T440 (I have the T440s) w/ 9 cell battery especially if your commute to and from work is large. Macbook Pro + VMFusion + VS results in < 2 hours battery life. It's much better to do native Windows 8.1 and then VMware OSX.

You'll get 8-10 hours battery life (under load, else 16 hours), touch screen Windows 8, touch screen OSX/iOS simulator, touch screen Android simulator and touch screen Windows 8 Phone simulator - concurrently all at the same time.

This is my setup for cross-platform mobile dev using Xamarin. There's something special about commuting on the train, doing iOS/Droid/WP8 development in Visual Studio without being chained to a physical mac-mini or multiple computers.

You don't need to run Windows in a VM, you can run it natively with Bootcamp (which boots into the image on a separate partition, as you would do on any multi-os computer).

But still, if you are using it primarily as a windows machine, definitely get a windows machine because it will likely be cheaper.

New models are expected to come out soon, so if possible I would wait for a bit: http://buyersguide.macrumors.com/#Mac

I was in a similar situation last year (coming form an old MBA) and I decided to go with the Pro. The weight difference is not huge but noticeable. In terms of performance you don't need to worry about the Air, it'll be able to handle everything just fine. What really sold me on the Pro was the retina display. Beautiful. Once used to it it's really hard to go back to non-retina. What the Macbook Air has going for it is slightly longer battery life. So, I'd look at it as tradeoff between retina display and battery life. Don't even worry about performance.

Pro has more power. The big projects will need it. I chose a pro when I was doing my iOS stuff as my mate has an air and Xcode just killed his resources when running the app simulator.

That's interesting to know, does the Pro perform well with XCode or is it so-so? I'm interested in looking into iOS dev with the release of Swift so XCode is something else I'll need to keep in mind.

Yeah the pro performs very well for me. If you are wanting to get into Swift there are some awesome beginner tutorials here: http://ios-blog.co.uk/swift-tutorials/

Yes, get the pro. Get the 13'', with 16GB ram, and connect 2 large 27'' monitors.

My current development machine is a MBPR utilizing the 2.3 GHz processor & 16 GB of ram with Parallel, Windows 8.1 64 Bit, and VS 2013 Professional without issue.

We chose the MBPR displays because we could pick them up the next day and didn't have to wait on the build time for the T440s. I cannot say I didn't really look at those, but I did and would have probably purchased those if we weren't on such a time crunch.

I was in the exact situation before, and landed with an Air (top spec).

It really depends on what things you wanna run on it. A VS, even inside a VM, the Air can handle the job easily. But if you want to run more programs on it, it will burn!

The upside of Air is the battery is awesome endless, giving that you don't have a lot programs running. On the other hand, and is the reason why I'd choose a Pro in the future, the retina screen!

Generally if I'm in my dev environment then it'll be Visual Studio, SQL Server and a web browser that's typically open.

The battery is a definite win for the Air, do you know if it gets similar battery life in Bootcamp? I know there are optimizations in OS X designed to improve battery..

I originally thought that weight might give the Air an advantage since I'll be carrying it every day but it seemed like a non-issue when I went into Stormfront so I'm tied!

I was in a similar situation last year - but after visiting the apple store and trying the different variations I ended up going for the 15" pro, i7 quad-core, 16GB RAM, 512SSD and the retina display with 2880 x 1800 resolution.

It does cost more than the other 2 options but if you are a developer, it might be worth it.

I'd get a Pro and use OSX BootCamp to dual boot.

My i5 Air, however, has a turbo boost option that up the processor speed from 1.7ghz to 3.7ghz when it's needed, and it's very fast comparing to my i5 lenovo running anything because of SSD.

I use a pro retina 15" as my windows Dev machine.I boot to Windows (boot camp). There is no need to run parallels or VM if you don't need OSx simultaneously.

You'll want the 16GB ram on the bigger one if you are running any databases locally. Otherwise, 8GB will work.

Did you consider the Yoga? It looks pretty competitive.

I'll be looking at running it as OS X primarily since I'm heavily in that ecosystem and prefer it to Windows, I'll just be bootcamping from time-to-time for my .NET development :)