pygame is richly active, witness the Aug release of 1.9 with nokia s60 support, enhanced py2app/py2exe support, and a bevvy of experimental features (support for Python 3.1, webcams, gfx, …). Books like Hello World and periodic, fun competitions like ludumdare and pyweek bear witness to the vitality of its community and ecosystem.
pyglet has a neat, newer API, and is convenient (pure Python, BSD license instead of LGPL).
As for speed, I’ve run no benchmarks but I gather that out of the box pyglet is better at exploiting advanced HW acceleration for 3D work, while pygame is better at 2D work and on HW that’s nowhere as advanced (smart phones, netbooks, etc, don’t have shiny 3D HW accelerators). You can enhance both frameworks’ speed with add-ons, though that does lose convenience.
In terms of Py3 support etc, I believe the issue is simply that pygame, much more mature and popular, has a vastly larger core development group, so of course it can get new things like Py3 support out of the gate earlier.
If none of the above issues is decisive for you (you’re fine with LGPL vs BSD, don’t care much about smartphones, need no books, etc, etc), the only sensible approach is really to download both and try the same elementary tasks of your interest on machines of your interest — that will tell you how well each “fits your brain”, your need for speed, convenience, and so forth.