@Ministryofgiraffes
I just spent a month in Indonesia and did something very similar to you. I started off in Ambon at Dive Into Ambon for 7 days of diving then hopped onto the Mermaid 1 for the Ring of Fire trip for 12 days which is basically the Biodiversity trip without the Raja Ampat section. I finished by returning to Komodo for a 7 day liveaboard. (The only thing that would have made this more perfect would have been to return to Raja Ampat for a 12 day then finish by also returning to Lembeh. I know I'm being greedy!)
Something to note which
@dirtfarmer just touched upon. This year's conditions were really rough. We set off in early Oct and thankfully, Mermaid 1 has a steel hull. I met a few folks that went on the Ambai a few days before we set sail and they had to turn around due to the 2-3 meter swells. They were unable to continue on their itinerary through the Banda arc as reported to me by a guest on the boat. She also mentioned that the Seahorse was also out there this year and had to stay put due to the conditions. Our sailing went as scheduled, but the first couple of days were rough. Multiple people were throwing up and no one slept. I've been on many liveaboards and have been on open water crossings before and this was one of the roughest, if not the roughest. Our overnight crossing that should have taken 12 hours ended up taking closer to 17 or 18 due to the conditions. We were at least able to do it. Because so many boats had to change their plans, we ended up having many if not most of the dive sites and volcanic islands to ourselves. Just keep this in mind when you are selecting your boat that conditions can throw your trip sideways, though this year is not "normal" is what I'm reading. Of the boats you listed, only the Blue Manta is a steel hull.
With that said, your itinerary on the Biodiversity trip only does a few days in Raja which I don't feel is enough. Rather than do a repeat of the Ring of Fire portion of your trip, I would suggest going with the Ilike for the itinerary (Raja Ampat and Triton, something new and more of Raja). I've been to Raja Ampat twice and am returning a 3rd time in April to sail with the Ambai - others that have been on it have said good things about it, including someone I know that runs trips for a travel agency. I do know a divemaster on the Ilike and have also read good things about them.
Some folks here did a Banda crossing with Blue Manta recently:
Real Time Blue Manta Review: Banda Sea 9 – 19 Sept 2019
Some of my main concerns that I have also heard outside of Scubaboard are that the DMs are not that experienced with the specific dive sites or areas which would be consistent with what was reported to me by a friend that was on that boat - a group spent a lot of time essentially looking at sand. Bummer for the amount they charge. They had a few issues on that sailing so do read the thread.
Something you may want to do is ask each of them their dive policies - for buddy groups and for max dive times. You never know who may end up with you in your group and how it might affect your dive times and profiles. That may also move the needle for you. The Mermaid states 70 minutes for day dives and 60 minutes for night dives and were very flexible if we didn't have to do a crossing or have anywhere to go. I had some 80 minute dives.
Essentially, over a period of 12 days and 3-4 dives a day, that is a lot of added time underwater and essentially extra dives.
