Thanks for all the useful comments.
There are some columns that use forumulas, but basic financial stuff, nothing to scream about
I tried Windows 7 version of Excel 2010 via VMWare and that works absolutely fine. But the RAM is totally maxed out right up to 2GB. So that's a problem.
So I think both solutions would do the trick. The new MBP processor would help me run Office native, and 4GB MPA would allow me to run windows
So I'm still 50/50. I'm could get the MBP with 3rd party SSD added asap, for about the same price as the 4GB MPA.
I think I would like both machines
I am off to the apple store in an hour or so to trade, and will have a play with the MPB but it will not really be fair comparison without the added SSD.
All opinions very welcome on which I should go for, given my need for Excel.