Whats the difference between having all electric vs all gas appliances? cost wise?

I’m looking at Condos right now one has a gas furnace and water tank, while the other 2 have an electric(forced air) furnace and an electric water heater.
Which is more expensive to run in terms of energy bills? Do Electric Furnaces last longer then gas? Are they cheaper to replace? Does an electric furnace use a heating element or what?(vs a gas using a flame)

The one I’m looking at still has an electric furnace from the mid 70′s. Should i be worried?

I thought this comparison chart was interesting.

http://michaelbluejay.com/electricity/gas.html