What matters in a hdmi cable? – cable gauge can matter if you are going long. quality of the termination, quality and design of the stress relief on the connector, weight and stiffness of the cable, fit and tolerance of the connector… many variables at play.
Will motion blur be a problem with certain hdmi cables? – no, motion blur is inherent in the Source content and exacerbated by poor processing in your Display device.
If a cable is causing a problem in your system you will suffer random sparkles, intermittent drop-out or no signal, it won’t cause image ‘degradation’ in the way a poor cable can effect a pre HDMI system.
Look for a High Speed cable from a reputable supplier.
Joe