For running Windows via VM Fusion?

My guess would be not at all for Office, perhaps minor for the others. The i5 performs very well as a Windows machine under Parallels. I assume results would be similar for Fusion

 

Office, not really, Adobe suite will range from not really to helps a fair bit. And I would say AutoCad would see some benefit from the i7.

I guess the real question is how long do you plan to kee pthe Air for? if you plan on a few years it could be worth it to get the i7. Otherwise it's your call on which processor.

 

Unless you're doing BIG things in Autocad, I suspect you won't notice much difference CPU wise.

I have friends who are using far slower machines on big oil and gas pipeline projects, and most of their speed issues is with the version control system, not the PC they are using.

Just be aware, if you have 8 GB of RAM, OS X will need a couple of that; you won't be able to allocate 8 GB to Windows.

I haven't used Autocad myself for a long time, but I'd be tempted to go for either a Retina or cMBP and get 16GB in there to have a bit more headroom.

If you're planning to be running CAD VMs on this machine during its life, I think only 8 GB of RAM is likely to become a bottleneck within the next 3 years (RAM prices have tumbled - and that means application developers WILL consume it).

If you're only planning to keep the machine for 12 months.... carry on

 

No. Just make sure you go for the 8GB option and as much HDD as you can afford.

 

Actually, yes.

The i7 will scale upwards if and when you need the horsepower. Windows is notoriously inefficient and can use the extra horses.

For $150US, its a no-brainer.

The power is there if you need it.