My first think was the same. The metal one will be heavier but stronger. After them I looked at the details. Both of them are for the planes up to 12 kg!
So, how could it be stronger?
http://www.hobbyking.com/hobbyking/s..._10mm_Pin.html
http://www.hobbyking.com/hobbyking/s...unt_2pcs_.html
It looks like, the only differences are the weight and price.
