One thing to note when building with commanders like these two is that they are both hard answers to a very popular kind of EDH deck.

Having access to green and white opens up powerful tools, like Greater Good, Death's Oasis, and Hogaak, Arisen Necropolis. I'm slightly more in favor of Anafenza, the Foremost, however. Mono-black gives you access to Gravecrawler and Bloodghast, as well as plenty of tools to mill through your library.

Not only will he exile enemy creatures instead of letting them die, he's also a sacrifice outlet in the command zone. Kalitas, Traitor of Ghet is a strong contender. That being said, rather than rely on a single card in your deck to protect Bridge from Below, there are several potential commanders that can fulfill the same purpose. If your opponents' creatures are exiled as they die, then your Bridge effects will never see them hit the graveyard. When I started looking for decklists with Bridge from Below or Magus of the Bridge, one card was repeatedly mentioned as the best way to keep them in the graveyard (or in play, respectively): Leyline of the Void.

Edh sidisi brood tyrant dredge