Need to buy a chainsaw for very occasional use to deal with the occasional fallen tree, fire wood etc...

Would a 14 " chainsaw be adequate for this use... or should I go bigger? I obviously do not want to buy a saw that is useless but I am also looking to save a buck since I may only use it occasionally and spend more of my money on other tools

That evaluation should be based on the maximum diameter expected and the type of wood. OAK being a harder wood.

You can also consider electric, but it may not be a good idea for firewood.

More than inches you should be looking at brands. I'd go 16" simply because I run into larger trees and 16 is an all around good size. Stihl Chain Saws - Professional Chainsaws, Fire & Rescue Chainsaws, Electric Chainsaws - STIHL USA (http://www.stihlusa.com/chainsaws/) and Husqvarna Powerful Robust Saws for Professionals | Husqvarna Chainsaws (http://www.husqvarna.com/us/forest/products/powerful-robust-saws/husqvarna-chainsaws-powerful-robust-saws/) are very good brands