Answered by Shaykh Faraz Rabbani
For a man outside of prayer, is it preferred that he wear loose slacks, or that he cover using a longer shirt? What can one say about jeans, as they usually cover in a more form-fitting way? And if a man is outside of an environment in which he needs to wear certain clothing a certain way, is it better for him to leave his shirt untucked, or to leave a suit on? Perhaps you have noticed that our men are less inclined to dress modestly than to instruct their womenfolk how to dress. It annoys us women to no end.
Walaikum assalam,
It is better to have loose slacks AND something (whether a longer shirt, or a coat or jacket) that covers his rear.
Somewhat tight jeans would be at least somewhat disliked and blameworthy. Form-fitting jeans that fully define the shape and form of the awra during normal wear would be sinful to wear and prohibitively disliked.
Men have to obey Allah about dress just like women do.
Wassalam,
Faraz