Вот нашла описание сравнения C910 и C920. В общем надо C920 только, так как поддерживает аппаратную обработку H.264.
Major differences between the C910 and the C920 web cameras:
C920 has built-in H.264 compression, thus releasing the burden of H.264 processing from your CPU. However, it seems that the compression can only be seen by the Logitech software and not by third party software. That's unfortunate, because that makes one of the best features of the camera useless.
The C910 does not have H.264 compression built-in.
The C920 is 1080p.
The C910 is 720p.
The C920 has a tripod mount.
The C910 does not have a tripod mount.
The C920 has a 3 megapixel sensor.
The C910 has a 5 megapixel sensor.
--I know, you would think that the C920 would have the higher megapixel sensor. But then again, it only takes 1.5 megapixel for 720p video.
Источник
http://forum.ibroadcastnetwork.org/s...the-Difference
p.s Есть еще C930E интересно как себя показывает по сравнению с 920.