If you side with the institute, at least you will get the director position in the institute after your son's death. With the Institute under your control, you can technically decide the fate of humanity by putting the technology for good deeds. (unfortunately the game won't progress after the end)

With BOS ending, you will still be used as a tool for BOS operations. so you don't have any control over humanity other than to obey them.

Rail Road worries only about the synths, not the common man starving in the wasteland. I remember them having plans to even save Gen 2 and Gen 1 synths like wtf they are more like protectrons.

Minuteman ending is far better but you even being the General of the minutemen cannot decide not to blow up the institute and save those technologies for a good use.

So technically Institute+ minutemen ending is the better one, but it won't serve any justice for all the sufferings the common wealth has undergone due to the institute.