Are bioeng. programs harder overall to get into than materials engineering?

[tissue engineer 2012]

I majored in materials with a biomaterials focus in undergrad. I was going to apply to materials PhD programs but am thinking now that I would like to focus mostly on bioengineering and should maybe apply to bioeng. programs instead.

Overall, are there more people applying to bioengineering PhD programs than materials, i.e. is it more competitive? Would it be in my best interest to stick to materials and just try and do some interdisciplinary work in bioengineering?

I don't have a very good GPA (3.2) so I am trying to be smart about where I apply, and under what program...thank you for your time!