I stuck with some question. What the difference in the use of Boostrap 4 or Bootstrap UI(base on v4.0.0-alpha.6) powered by Angular in developing application on Angular 2 ? Does BootstrapUI have some must have stuff that clear Bootstrap 4 doesn't have ?
Bootstrap UI isn't a straight wrapper for Bootstrap JS-based behavior, it's a rewrite of that behavior in Angular, so no Bootstrap or jQuery dependency, just the bootstrap-css-only node module, which is purely a copy of the Bootstrap CSS. Thus, if you are using Angular correctly, most of the Bootstrap components will not work. You will need to write your own directives to get them to work. So it may be easier to use Angular Bootstrap which does all the work for you (Source).