Weather this year was rough in the Banda Sea in late-September to early-October. This year I did the crossing (Maumere - Ambon) on the huge Mutiara Laut Sept 27 - Oct 8....last year I did the crossing (Maumere - Ambon) on the tiny Tidak Apapa October 2-16....so pretty much same time of year for both trips.
Last year water temperature in the Banda Sea was 27 degrees Celsius, no wind, no rain and flat sea.
This year water temperature was 24 degrees Celsius, strong winds and big waves (some nights waves up to 3 m (10ft)).
This year we could not dive Nil Desperandum, Manuk, Hatta and Nusa Laut due to the wind and waves.
Last year we had schooling hammerheads at Manuk. This year we had schooling hammerheads at Serua and Suanggi.
Mutiara Laut insisted on 2 days of diving Alor which I found silly - I agree with Luko that Alor is best dived with a local dive center (very strong and tricky tidally dependent currents). If a liveaboard does want to dive Alor I would say stick to doing 2-3 shallow no-current dives for the rhinopias.
When next time I return for a liveaboard in the Banda Sea I think that I will look for a 10-12 day Oct-Nov Ambon - Ambon itinerary that includes Banda Neira, Manuk, Serua and Nil Desperandum (furthest south)...but leaves out anything south of Nil Desperandum (Alor, Niita/Wetar, etc.).
Plus points this year: Huge sturdy boat (48m (140ft)) that could handle the waves...still in the high sea some porcelain/plates were smashed (luckily no cameras) and 1-2 guests got hurt a little falling over and by doors.
Also a nice 3 hour land excursion on Banda Neira. In fact I liked Banda Neira so much that I am thinking of returning in March for 12 days there diving with a local dive center and just enjoying the island....but chances for hammerheads are reportedly not great that time of year, though the weather March-April is usually quite calm and fine I am told...and then finish up with 5-6 days Ambon for the muck diving. I cannot find any liveaboards doing Ambon - Ambon in March-April, but as mentioned I liked Banda Neira so much that I think that I will be quite happy with just landbased diving. Flights to Indonesia seem good value March-April (probably because Bali etc is then not in high season).
P.S. - I heard 2 liveaboards sunk in bad weather in the Banda Sea March 2019...luckily with no fatalities I was told. So maybe that and the schools of hammerheads being out of season March-April (deep thermocline) is the reason I cannot find any Banda Sea (Ambon - Ambon) liveaboards in March-April 2020.