ينبغي :means favor to do something ينبغي تناول الافطار يجب: means must to do something يجب ان لا تكذب الهاء:connected conscience على/لـboth of them prepositions and there different between them of meaning in a sentence like when they linked with connected conscience it's means له:someone or himself do something to him عليه:he do something to someone يجب عليه ان يؤدي صلواته ينبغي له ان ينام باكرا But when عليهcome whithينيغي it's meaning must do something ينبغي عليه ان يقوم بواجبه المنزلي يجب عليه ان يقوم بواجبه المنزلي

السلام عليكم The both we use them for the same case, therefore the more common and that we use in يجب عليه أن يجب عليه+ المصدر This is a smaller difference between them, the second with lahu we sometimes use for a reason of for someone or something for example: أمور كثيرة يجب له أن يحترمها many things he should respect them. Here I meant by using la لَــ the things what he should care about. But rarely when we use يجب له أن | يجب له + المصدر The important is to know how using them. :) و الله أعلى و أعلم

يجب (must) , ينبغي ( should)

عليه in common

For لـ &على here the differences : لـ is mean : for (in this case ) exp: يجب له أن يدرس this means : he should study / this advice is for the person to help him but يجب عليه أن يدرس this means : he has to study / this is order not advice or request and the person has to do this thing . nothing is more common we use both according to the meaning . I hope this will help you