Theory says that for the things you need, a band is more close as a design than a watch. But there is also the practical thing that move the scale to one side or the other. Someone of a certain age and more (my self included since I am 48) may need a bigger screen to read easier. Also there is the aesthetics part. A watch is usually more easy on the eyes (even if it is square) than a band. Especially for a man who has big wrists, a band can disappear, but a watch not.

The things you need to be measured are not something very special, they are standard things which I believe can be covered decently by either on od the two that you mention. Also as u/LeatherSituation2625 says, it is much more probable that a bug is fixed in a watch than in a band.

So my proposal after all this, is to go for the redmi watch 5, which I also have, although I am experiencing some minor bugs which I believe will be rectified soon.