Those are the only two. If you're considering Roatan - you might check with the MV Pearl off Utila instead. It's boooked thru DivEncounters.
Honduras Bay Islands Live-Aboard Diving | DivEncounters Alliance Live-Aboard Diving - it's the renamed Utila Aggressor. IDK their current route but when it was an Aggressor they started there, moved over to Roatan for a couple days, out to the sea mounts then back to Utila. Nice boat, we rode by it once moored at the Halliburton wreck south of town.
If you dive at any of the AI resorts (Cocoview, Fantasy Island, Anthony's Key, Reef House) on Roatan finding buddies won't be an issue - you'll be assigned a boat for the week. If you plan to shore dive, you'll need to stay at one of them anyway - they have about the only shore dives and tank rental elsewhere is basically impossible. You won't have a problem grabbing a tank and walking in off Cocoview's dock solo. They also drop you on their house reef/wall/wreck dive every 2nd dive.
If you're interested in deep wall, very sharky, very lush coral reef diving consider Explorer Ventures Turks/Caicos trip also. They have availability your week and finding a buddy on-board won't be a problem. The crew will always dive with you if needed but you'll likely have a single room-mate also. We dove 2,3,5 and once or twice as a group of 8. Met everyone on board except my buddy.
Explorer Ventures: Adventures in Liveaboard Diving Early morning flight connecting thru CLT and you can get there the same morning from the west coast - I live in Phoenix and we were on Provo (Providenciales) by 1PM.
Here's what you can expect - Mike was on the boat about a year before us. The only thing that's changed is they now need you off the boat at 9AM Sat. - we just waited around at the airport most of the morning.
Saudio's Trip Reports
Aggressor does the same basic run - I didn't look at their availability. Explorer might be a little cheaper.