OF is probably better supported by third party developers etc when it comes to plugins and so on from my experience with both. I personally opted for OpenFrameworks as my C++ library of choice after playing around with both for a couple of years.

To be honest though these days I think a lot of people have moved on to visual programming tools like TouchDesigner/VVVV/Notch as it's so much faster to get creative out the door with those and you still get glsl shaders and C++ integration with them.

Saying that with TouchDesigner and Notch youre paying (and in notch's case quite a lot), you can't distribute and files are heavy but when doing interactive installs and shows the benefits far outweigh the price and time saved so we use those tools far more than libraries these days.