Main partition on original Apple SSD or new Samsung PRO SSD in 2011 Macbook Pro? A few questions here relate to replacing the optical drive with an additional HD or SSD. Its time for this to happen on my MBP 15 inch (late 2011).

So I will effectively have: 


the original 256gb SSD where it was when I got the macbook
a new Samsung 840 Pro SSD in the DVD compartment


My question: which disk would you expect to fail sooner? I'm trying to decide where toput my OS and where to put my home directory etc...  Any thoughts or experience are helpful!
I don't think that this question can be answered with authority.

However, if you are worried about failure due to memory cells wear, we can speculate. Every thing else being equal I would expect the SDD disk to last longer. That's because the SSD controller tends to spread writes among the available memory cells, and the more cells available the less writes each cell will receive.

And of course I would expect a new drive to fail later than an old and used drive.

Then I would say that generaly speaking a newer and bigger SSD will last longer than an older and smaller one.