I've never had a problem with an integrated seat binder on a steel frame.

Both the Thunderdome and the AC 364 are very nice but they're different bikes made from different metal. I haven't really ridden the Look much because I'm still nursing some broken bones but from what I can tell from cruising around the neighborhood, the Look rides like a nice steel frame.

Info about the type of steel and a link to the geo chart is on the Retrogression site.