Whichever will do best to insure that my LED's don't exceed their optimum operating temperature. The reason I posted this was to get an indication as to what that temperature may be but I'm also open to varying methods of regulation.
it is kinda hard to mesure temp of smd leds on strip, if i had to i would use contact probe thermometer, (not ir thermometer), i would take readings right at the solder point of the led, (if the tape is not waterproof\silicone enveloped, if it is , i would open small section) and would turn your fan, when temp gets 70C. or i would get one of those thermal switches that are NO, and place it right under led, i would use 65c switch, you can splice it into power feed, of your fan, just make sure current rating of thermostat is not less of your circuit, or it'll close once, and will most likely get stock, and wont open anymore.
but to avoid all that, you can run strip at 9v instead of 12, and you wont have to worry about temp. i've done it may times like that, no heat issues, unlike driving them at 12v where i had many thermal issues.
Thank you for that suggestion. A quick Google tells me that step down devices are inexpensive so I will order one and test my components to see if I can get the necessary intensity at 9V. Since I have the power available I may even add more LED strips to make up for any lost intensity.
This is in an area where fan noise would have been a concern and if the 9V supplies the necessary intensity the problem is solved.