I don't want to take over Sascha's build thread but I will make a quick comment on it.
I think mortality rates have to do with more on the source of the frag, which is obvious but I wanted to mention anyways. Obviously, the best frags are from fellow reefers who've had the coral in their system for a long period of time and it has shown great health and growth in their system. Even better, a system similar to your own, as far as lighting and water parameters are concerned... so the transition is as smooth as can be. I always feel bad when new reefers decide to try SPS and start ordering from some of our online vendors with fantastic photos of their SPS. Most of those SPS are mariculture and are not used to life in a reef tank. The transition is hard enough on its own but to do it in a newer system with a hobbiest that is new to SPS can spell disaster sometimes. Also, the colors you see in the picture will most often not keep so I typically discourage buying mariculture based on coloration you see in the pictures. Think of them as more to a hint as to some of the potential but know for the most part it will not stay that way. It may blossom to even something more beautiful or really, it's just a regular SPS you can get at the store but it looks amazing when it first shows up from the ocean. I encourage anybody looking to try SPS to get a few tester pieces from a fellow reefer in town to test your tank out first and then start opening up to purchasing online or at a LFS.
But to answer your question, with all external criteria constant, I feel the bigger the better. Mainly because, if things turn south, you can always frag up a colony and try to save the pieces. Superglue and clippers are your friend. I'd think that Sam has a lot more experience to offer in this regard though as my old system was comprised mainly of frags from fellow reefers and mariculture colonies are newer to me in this new system. Sam has been doing maricultures for a long time now and I'm sure he has great wealth of experience to share in their regards.