call it in the air. head or tails...
anyone who offers a more certain answer is making it up.
the only one who can answer the question you asked is you and only after testing with the equipment it will be used on. factory matched RAM is tested at the factory and unless using a matched set its a gamble and gambling rarely works for me.
I suggest replacement with larger sets rather than trying to match 2 different sticks.
insert the RAM and run for 5 passes through memtest 86. no errors or reboots and it should be fine. if you do get blue screens or other errors it may be worth a 12 pass test. testing will take the better part of a day. 16-24 hours in my experience