I'm pretty agnostic on this debate. I like baby backs and SLC's. Usually comes down to what's available in my grocery store and how they look. I'm not a smart man nor a talented man, but my ribs kick ass regardless of type.
My local Sam's switched to Smithfield 3 packs of back ribs about a month ago. They were OK, but sure weren't as meaty as the IBP brand they had always had. Last weekend, I saw they switched back - woo hoo! The 3 pack was more than a pound heavier than the Smithfields (9.64 lbs for 3 racks). There was SO much meat on them I darn near had to get out a knife and cut them like a steak! lol.
I've said all that to say it only reaffirmed my preference for back ribs over spares! They were awesome!