All bolts used in any climb should be stainless steel, regardless of type. It is no use putting up a bolted route and have it rust out in a few years. At Crag X we use stainless steel ring bolts supplied from a guy at Penrith, NSW. The main reason we use glue-ins is because we bolt on sandstone, and expansion bolts over time can loosen in the soft rock, and since they require glue too, we went for rings because they are easier to clip than hangers. The negative side of glue-ins is that you have to wait at least 48 hours before you can climb the route, but generally after you have bolted a route you are too stuffed to climb it anyway.
The phone number of the Penrith guy I get the bolts from is, Rock And Rope Engineering (02) 47290621 from memory they cost about $200 for 50, ie $4 each. Another alternative is expansion bolts and hangers but I don't know much about them and would be grateful for any information.