For every car I've installed a radio in the last 30 years or so, the primary consideration was form factor. Deciding where the radio would go, and narrowing the search field based solely on dimensions. From there, single, dual band, dual RX, half/full duplex and other features became the final decision. If you have any interest in "digital" (DMR, DStar, Fusion, NXT, P25, etc) then you may have to compromise on size, as there are limited models that support these specialized modes. I've traveled a bit with DStar and DMR and can't say it's a hill to die on. I would rather have a "nice" dual band FM rig, though as time goes on the feature set has blended a bit. I have both an 8800 and 8900 and like what that style of rig offers - deep feature set, computer programmable, both dash mount and remote head mountable. The only dig I would say is the display is small (goes with the form factor). If you have the option to install a rig with a larger display or remote head with larger display, readability is a bonus. Once you get past the ergonomics and digital capable, I would consider the rest of minimal consequence as all radios will have nominally all the same performance and feature sets.
Mark K5LXP
Albuquerque, NM