I'm very sorry, ETenebris. I had a best friend taken from me, too. I like either necklace; they are each beautiful and fitting to wear as a lovely memorial to your friend.
I think you should choose whichever size suits you. I'm leaning toward the one on the right, but it's definitely a personal decision. I didn't even know they made memorial jewelry. It's a lovely idea.
Hugs, so sorry for your loss. Either is lovely. You know the Victorians would keep a lock of hair or a picture in a locket to remember people by, I think its a beautiful remembrance.