Well the Kenwood has a volume knob and I'm the type of person who wants a volume knob instead of a button, it also has a bit smaller screen but it is also less expensive.
The Alpine has a bigger screen and comes with a backup night vision-capable camera which I like, so it is up to you if you want to spend the extra $170 to get the Apline.
If you got money then go with the Alpine, the volume knob thing is getting faded out because they can wear out or get lose after a lot of usage.