light, tough, good shape
i-beam is less common
The I beam should be more common in my opinion since it saves a bunch of weight and is super strong. The kevlar sides on the Bel-Air are tough and will keep it from getting thrashed when the bike meets the ground from time to time (aka crashes). The Bel-air has a shape that fits me well and so I don't mind spending a few hours pedaling on a trail with it.. So, in the chance that you don't have to get a railed saddle to match your traditional post, consider a go on the i-beam system and this saddle. If you're stuck with rails, SDG makes a railed version as well.