Cast iron all the way , wouldn't have it any other way. We recently purchased an 1850 farm house 2000 sq ft. that was being heated with 2 space heaters. House has never been insulated and has the original windows. We are planning on keeping the interior pretty much all original but didn't really want the big radiators we had in the last house. I was able to buy enough cast iron base board on CL to do the entire house for $300. It looks like it was always here. They get hot and stay hot. I used long pieces of 6" tall in the bigger rooms and 9"shorter pieces in the smaller rooms. I have 2 3/4" pex loops with 1/2" supply and return lines with monoflow tees. Most of the 1/2" runs are under 4'. There was a little lag in getting everything warmed up in the beginning but now I am getting pretty even heat in all the base board (checking with my hand) been meaning to put the infrared on them and see how much I am loosing at the last part of the bigger loop. I also put valves on a few of the supply ends in case I ever wanted to dampen them down if some rooms were getting too much heat.