i'm with Tricia. probably doesn't matter. will depend on how tightly you pull the thread through when you're stitching. if you pull it too tight when you go around the block, you could create a slight bubble in the middle.
don't ask how i know that. i just heard it somewhere. i would NEVER make a "mistake" like that. well ... almost never. LOL :roll:
try one block each way and decide which works best for you.