I think either would cross well with them. Both would make nice replacements or feeders whichever route you were wanting to take. The Hereford would give you the most bang for your buck with the Heterosis with the calves. You might get some red calves now and then and possibly some horns depending on if your cows were red carriers and the horn genes on the bull. The Angus bull would give you some nice solid black calves with less leather.
If you are selling to the local sale barn, call them and ask them what cross they recommend. If you are selling replacements, look at what people are buying. If you are selling to the 4H / FFA kids, ask the extension agent what they need.
Some areas, at the sale barn the stocker / feeder buyers prefer Brangus Baldies. Other areas prefer smokies (Brangus - Charolais). Others prefer red baldies. Ask who are plan to sell to what they want.