Can I toss in a vote for 'ask the crew on the boat?'
Here's why. Things change from day to day, and even from hour to hour. The crew might have some recent info (from a day or two ago, or even minutes ago from another dive boat via the radio). Some days I would pick the Spar, and on other days I would pick the Papoose.
The Spar can be really great or really so-so. When it has nice blue water, it's an easy (by NC standards) enjoyable dive. At times though, there can be a stiff murky layer of curent on the bottom that saps visibility and makes the dive more of a chore.
The Papoose is a further out (longer ride) and deeper (less dive time), but more consistent. The real wreck aspect is nice, but you're looking at the bottom of the hull for a lot of it and that's not quite as exciting.
If you make it to the Spar, you can sneak up to the front of the wreck and check for bigger sharks under the bow. You can also sit on the main deck and watch the sand tigers circle. Just sit and watch, they will swim a circuit.
On the Papoose, and your DM where the sharks are on that day. You can sit on top of the wreck (on the keel) and look down from above or you can drop down to the sand and watch.
It's easy to find teeth on both wrecks if you know where to look. I have good luck on the main buoy deck of the SPAR. Teeth on the Papoose tend to get fall down and caught on the ridges that run from bow to stern along the bottom of the hull.
Good luck with the trip. There are worse places to be stuck for a day if the weather doesn't cooperate.