I'm getting the soft cap. Reasons:
1. I think it looks waay cooler. Seriously. They're ridiculously hot.
2. Graduated from uni in June so have done the mortarboard thing already. I still have my mortarboard so I wouldn't buy a second even if the oxford one is different. what'd I do with 2 mortarboards, let alone the one that's been sitting around all summer already?
3. In the states (where I studied) only the PhDs (and not even masters, law, dental, med or business grads) get to wear soft caps (males and females). we had a procession of whole lot of big-shot academic dons from other unis, and european unis and they all had soft caps - some of them with some pretty cool colored trim and fancy tassles. It was pretty cool - they looked so academic. We were so jealous!
4. I can show it off to my friends. :-)
I hope some of y'all join the soft cap camp. I'll, nonetheless, wear mine with great pride. I wouldn't wear it indoors though.