Cat6 is backward compatible. I like the fact it's usually 23 gauge vs 24 on
cat5e. Not much difference unless you go with stp w/drain wire. For underground I pay a little extra for the flooded. If I go Arial I get 5e or 6 with the messenger & uv protection. If you need it in a box 500 ft at a time may be the way to go on "outdoor" which I think only gives you the advantage of uv protection. If the jacket is hard the connectors are more difficult to install. It's best to consider everything.
The old saying goes don't fuk with the physical layer. Nothing causes more trouble than poorly installed transport medium.
I've recently ran accross cameras that are too noisy, due from cameras designed to use coax with the power leads outside the shield being supported on cat5e with baluns on each end and two pair used for the 12v power. This causes a noise issue more times than not from the 12v power running along with the video signal. (especially on metal blds) I've either had to replace the cable with a siamese coax or power it with another separate cable preferably close to the camera.
The bottom line, use the correct transport medium for the intended signal.