Excel 2003 or Excel 2007 modelling

I have been asked to write a macro/vba driven model for someone who only has Excel 2003.
I am currently using Excel 2007. Although I know there is backward compatability. Would it be easier for me to do it in Excel 2003 (as I still have a copy).

I am an experienced user of Excel but not with so much programming experience.

Advice would be welcome - thanks