I have owned both and towed both with the same tow cars. No difference in towing. Both were stable at speeds up to 85-90 mph. (Note, my comments are based on the trailers I have owned, mid 1990's vintage Cobra and Avionic.)

Avionic
pro: slightly lighter, less expensive, good service from Windpath
con: possible for the wing root dolly to disengage from the tracks,
the ramp does not remain engaged to a track when it is deployed,
the front of the trailer is not as well set up for storage of
rigging gear.

pro: more attention to detail in construction and design making it
more "user friendly"
con: more expensive, the tongue wheel can slip down while towing

Advice:
Given comparable trailers (vintage, condition, options) for the same price, get the Cobra.

If money is a factor, get the Avionic.

P9