Need advice on lining pcgrowbox : Flat White Paint or Windshield Reflector??

Hi all!, I’ve got a question about lining the inside of a new pc grow box I’m building. I’ve seen a lot of comparisons of mylar vs just flat white paint but I’d like to avoid mylar if possible. I’m torn between white paint and car windshield reflector material (which I’m using in my current pc growbox).

Can anyone shed some light on which would be a better reflector of light?
Also since the windshield reflector stuff is abt 3mm thick, would it retain heat more? Temps are fine in my current setup, however I’m planning on using more light bulbs = more heat, so I was wondering if it would be better to go with white paint instead.
Any help is much appreciated!
Noobie grower here from near the equator in Asia, ;)
 
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