Health,
I don’t know why you think the gemara on 44 is the “main” gemara, which somehow renders the one on 101 obsolete. On 101, the gemara quotes the beraisa (posted above) which gives marrying someone (much) older or younger as an example of an ill-advised marriage. The gemara on 44 asks a question on the mishna which allows multiple yibums (from different brothers) because this would also be ill-advised. The two are in no way contradictory, and, in fact, the Tur (166) gives the former as an example.