When it comes to comparing accredited medical physics programs I'm not sure there's any absolute better or worse. Instead a lot depends on your personal preferences and what you hope to get out of the program. To the best of my knowledge, those are all good programs. So I think you have a choice between three good options.
I'm not sure that Penn has a PhD program, so if you're thinking of going for a PhD, you would have to change schools after the MSc. (Not that that's necessarily a bad thing). The stats for their MSc program graduates are here.
Duke has already published it's stats for it's class of 2016. It looks like they've also added an accredited imaging residency too, which is great if you're interested in that side of things..
Vanderbilt DMP program stats are here. I'm not sure that the DMP program pays the people that are enrolled in the residency component of their program, although you should look more deeply into the details here though as I don't know this for a fact. The median salary for residents across the US is about $50k. So you could be giving up a substantial amount of money. The advantage of that program though is that you don't have to stress about a residency. The medical physics residency match statics for 2016 are here. Roughly it looks like those who participated had a 1/2 probability of getting a position. That's better odds than last year, but still not great.