Avivo codecs are hardware acceleration friendly. So if for whatever reason, your current codecs arent using the GPU decode features, the AVIVO ones should force it.
I.e. on a slower computer, decoding 1080-MPEG2 material takes a lot of CPU when your GPU is more than capable? AVIVO should enable hardware acceleration and free up the CPU during that process.
That being said, it shouldn't affect PQ much. If you're having issues, use the CCC and adjust the options on the video page