In general 44/40 is more accurate than 45 Colt according to own experience and to target shooters compiting in Bullseye with historical weapons, or at least it seems easier to get an accurate load with it, but it is a matter of using a slow burning BP , a bullet weight that your gun likes, and a good original revolver to get top accuracy from 45 Colt with BP.
All 44s tend to be accurate....like 44 SW Russian, a favorite cartridge by top shooters of the time..
in Muzleloading revolvers, 44 is famous for being more accurate than 36 at 25 meters ( at lower distances, all cartridges seem equal...).
In general the 38 spl is specially accurate, more than 9mm. In most countries where ISSF is popular, getting 580 points and more out of 600 maximum in national ISSF Center Fire championships is usual (60 shots X 10 o'ring) with 38 spl wad. and 32 SW wad......while in 9mm calibre, scores are normally below 580 points.
32 SW and 7'62 Nagant and all calibers around that size like 7, 65 parabellum are specially accurate....the 25 meter Centerfire ISSF World record was stablished by Russian shooters using Toz 49 revolvers in 7,62 Nagant and remained unbeaten for years...until a German
shooter got 595 out of 600 points in 2015... probably with a 32 SW. wadcutter pistol.... It seems impossible...but he made it.
All British 455 and continental European 11 mm like French or Spanish calibers seem specially accurate mainly because they don't have huge cases and you can load a perfect ponderate load with them using minimum or no fillers. and also thanks to short cilinders with minimum free bore, ..it is also truth that there are no replicas available in those calibers and they are shot only in original revolvers, which in general, are more accurate than Italian replicas with BP.