Should I use 1 goal or 2 goals for different success pages?

I got out goal setup and working, but had a question. Generally when someone visits our site they purchase both products (2 products). Well they checkout using two different sites; therefore two differen success pages.

Should I use one goal for both success pages. Or should I create two goals. I am thinking I should create two goals. Because if I only use one goal on both checkout pages. It might exclude the 2nd conversion due to duplication?