Your'e question is a few months old, so I don't know if its still relevant:
"Wondering about hydronic vs. straight electric baseboard heaters: which is more energy efficient?"
I'll give my two cents anyway.
The electric baseboard heaters will be 100% efficient. No energy is wasted by an electric resistance coil. Unfortunately, the electricity generating process is only about 35% efficient. A lot of energy is wasted at the power plant and along the transmission lines. Also, electric heat is typically around 3 times as expensive as natural gas heat.
A hydronic heater (which requires a boiler) will be approximately 80% to 90% efficient, depending on the quality of the boiler you purchase. There may be some minor additional inefficiencies if hot water lines aren't well insulated when passing through unconditioned spaces, etc.
Taking into account the energy losses that occur during electricity generation and transmission, I would say that the hydronic system will be more efficient. Please note, none of my analysis includes the energy required for extraction and refining, which applies to both electricity and gas. I'm assuming the front end energy used for extraction is similar for both energy sources.
Hope this helps. I would go with the hydronic system. It might cost more to install than an electric system, but its cheaper to operate, and I don't like feeling like I can't do anything about the large amounts of electricity wasted before it even reaches my home.
Sorry for the delayed response. This is my first time actually logging in here (except to join). The new job is going great. I'm really working exclusively on commercial buildings now. I kind of miss working on homes.