A minyan got together to daven Shabbat Rosh Chodesh. Because a situation prevented them from the shul, 10 men davened shacharit and Hallel.
Later the shul became available and others who didn’t have a minyan said that the minyan people should have waited to say Hallel with all those who didn’t have a minyan.
The minyan people claim that Hallel goes together with shacharit and it couldn’t wait for a few hours later just to include a few more people.
(later when we did all get together in the shul we lean and davened mussaf).
With who is the judgment and why? Please provide sources so we can look this up.
If I understand your question correctly, you mean to ask if the preference of saying hallel with a minyan, overcomes the fact that hallel should be said together with shacharis. The minhag is to say kaddish tiskabel after hallel, because hallel is considered a part of shacharis, therefore according to those poskim that say that saying the kaddish after hallel for shacharis is meakev, it would seems that they should not have waited. As a side point, the poskim say that since hallel is part of shacharis that one should not eat before saying hallel. This is even though we can technically say hallel all day, that is in retrospect, if it wasn’t said, but l’chatcila it should be said together with shacharis. See sources
Shulchan Aruch O:CH 422-2, M:B ibid 16 Biur Halacha ibid D:H V’korin, Mishna Berura 423-1, Daas Torah 422-2, Maharsham 1-1. See Irgos Moshe O:CH 3-70 who argues on Maharsham.