I look at it, that tanks, are like cars. Some people like Ford, some like Chevy and some like Foreign. I also have both Faber and Worthington, and can't say one is better than the other. They both carry air and the both have served well. As for buoyancy characteristics, weight is weight. If it's not in the tank, then it is on your waist or BC or plate. It will take " X" amount of negative bouyancy to get you under no matter where it is on your person, dependent upon your suit or whatever. I would also buy the new tanks based on your costs analysis.