I totally understand how you feel... I'm a political science/international relations major, so I thought the 1 year track was intimidating as well. And although I've ultimately chosen to do a 2 year track instead, I made sure it was in a location where I am able to fully take advantage of those 2 years. I wouldn't want a 2 year program somewhere remote, because there aren't as many volunteer opportunities, or nearby labs, etc, as there are some place like Philly.
If the one year completion is important to you, then by all means, make that one of your main deciding factors... the important thing is that you do well wherever you go. Only you know your capabilities and what you can handle.
The good thing about Penn, if you take advantage of one of the linkages, is that you really are there 2 years, and then begin med school in the fall. There are enough linkages for 2 year completion that it's not limiting. And worse case scenario, you take a gap year but work in a lab, or in one of the hospitals to stay connected to medicine.
Even if you complete elsewhere in 1 year, if you don't make those linkages because you were so bogged down with work you didn't have time to study the MCAT/score high enough, or you decide you don't want one of the limited linkages, you are stuck with a gap yr anyway...
Sorry if I'm rambling. This is kind of the internal discussion I had with myself when deciding. I was comparing Penn to a smaller liberal arts school program nearby that I was accepted to.