Should I buy a single 2x8GB kit or two matching 2x4GB kits for better reliability?

A single 2x8GB kit is the safer bet. Memory controllers are picky, and even identical model numbers can have subtle chip differences causing crashes. Two sticks also stress the controller less than four, especially on older or budget boards. If you already own a 2x4GB kit, buying another matching one is worth trying, but for new purchases, go with 2x8GB — it’s cheaper per gigabyte, leaves upgrade slots open, and avoids headaches.