Is the house still on paper (i.e., not built)? If I was going to build a house, I'd use ICF blocks and manufactured panels for the floors and roof. You can get them with very substantial insulation factors, and the structure is pretty much immune to termites, carpenter ants. Very quiet, great thermal mass, very comfortable. Air infiltration is essentially non-existent if you do your doors and windows properly. Typical lag in heat soaking can be up to three days. One school in the upper mid-west used them to build a new gymnasium...cost them $100 for the season to heat it. The people and lights provided most of it.
Radiant heating is nice, but does not typically respond very quickly...if the house was going to be turned down for a couple of days in a row, it will take awhile to warm up. If you go with the ICF walls, once the concrete core is warm, it will stay that way a long time, but the same thing is true if it gets cold-soaked...it will be cold for a long time, too.
The benefit is, if the house is really well insulated, it won't take much to keep it warm.
An ICF walled house will be thicker than a typical wall. Some would like this as you could have deeper window sills for plants, etc.
I would also consider windows from VisionWall Technologies. They do more commercial windows than residential, but their technology goes really well with thick walls. If you've ever been to Germany, you might notice similarities to how the windows operate. Turn the handle 90-degrees, and you can tip the top in. Turn it 180-degrees, and you can open it like a door. really nice, since you can open them and not worry about rain or people from getting in (unless they break them, like any window). They are really thick, but there is no seal to break and the noble gas to leak out. They're at the top of the industry in efficiency.
Geothermal, like any heat pump, will have only warm air coming out the vents. If you use it to heat water, since that is normally cooler, it may be more comfortable. Heat pumps, like radiant heating (however you heat the water), both work better if you don't set back, or if you do, not by much.