a decent pair of jeans would give it a more casual look, while wearing black dress pants would definitely be more dressy. So i guess if ur going formal, i'd go with the black pants. I feel like if ur already putting on a tie, why not finish it with the dress pants.
you could try both on, take a picture, and post them in a different blog. then i could tell ya which looks better.
is this formal enough?
Jeans or pants?