@IanH you should generally go with the best cable that you can reasonably afford to make the connection less susceptible to corrosion and oxidation.
We always use shielded cable and have used CAT6a for the last 5 years, CAT 6 since in the mid 2000's and CAT 5e before that. We used type 1 before so I've never seen a CAT 4 or 5 cable being used for data in the last 25 years...
The higher powered APs do sometimes clock down even with shielded CAT6 cables if they are over 10 years old so I'd always over specify where you can.
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