Surface Pro 4 or install Windows on MacBook Air via Boot Camp?

I am currently in school and a lot of my class projects involve financial modeling in Excel. Unfortunately the 2011 MS Excel for Mac which I have, just doesn't cut it for some of the advanced stuff that I do. Windows and Office is the preferred combination for anyone working in the financial services industry.

So my question is, should I upgrade to the Surface Pro 4 when it launches later this month, or just install Windows on my MacBook Air? My MBA is 5 years old and still runs fine, but it is due for an upgrade (It still has a Core 2 Duo processor and 4GB RAM).

What are the chances that the Surface Pro 4 will be a compelling upgrade? If it turns out to be a great machine, it might just be enough to make me get it.