I’ve never gone diving with steel tanks but am min the process of doing some research to get some. From what I’ve gathered they are negatively buoyant towards the end of the dive so you shouldn’t have any issues with staying down. You should also theoretically be able to take off some weight as well. Are they high pressure tanks or low pressure tanks by the way? Here’s a good article on tanks.
http://www.scubagearreports.com/index.php/how-to-gear-buying/50-scuba-tanks.html
I’m sure others on here can give you better input from experience though.