Shuvo,
If we can assume that there are no feature reasons for choosing between any of the later releases for you then I would also assume that stability is the next reason for choosing an LTM version.
Whilst 11.5.1 has only been out 3/4 months it's now got 4 HFs so I would certainly recommend this as an option. 11.4.1 has been a out a lot longer and is, hence, more "baked" so is also a valid choice. It also has 4 HFs too.
If you're able to update HFs as and when they come along then I'd go for 11.5.1. If you can't, due to change windows, then I might suggest 11.4.1 in that case.
Hope this helps, I'm sure other DCers will have their view too on this.
N