What is the best replacement for radiant baseboard heaters that was installed in my house in the 1970's. Is the Gel or Silicone heaters on the market now worth the extra money? Thanks

All electric heaters operate at 100% efficiency so the oil,silicone,gel heaters are not more efficient than the cheaper ones.
The standard type heats up and allows the heat to flow into the room. The other type does the same thing but the heat is released a bit slower since the element has to heat the secondary source(oil,silicone,water) first before the heat is released. The more costly heaters work a bit smoother to release the heat is all.

If it were me I would just buy the standard units and leave the others for the rich people who have nothing else to do with there $$$.