~We now have a gas dryer, and i would never go back to electric. Gas is drying your clothes when u push "start", I think electric really does have a very slow warm up time.
Actually, electric heats up immediately (open NiChrome elemets) and gas takes one to two minutes to ignite (the glow-bar or chattter-box take some time), unless it has a standing pilot light.
In the grand scheme of things neither is significant.
Electric can be throught of as cleaner in terms lack of combusition fumes, bur dirtier in that if carbonzes lint.
Gas can be through of as dirtier, but less harsh, in that water-vapor is a byproduct of combustion. Don't like propane in that the tips of such flame are normally yellow-orange, a sign of carbon.
The overall differences between heat sources, I'd say is negligible.