7018 is sort of the gold standard for work that needs to meet "code" so that's why so many people use it. The problem is it only meets those "codes" when handled and stored properly (i.e stored in an oven). It will still seem to weld fine if not stored in an oven (on the outside) but if you open the weld and inspect it with a microscope you will see alot of crystallization and porosity.
If you plan on just chucking the open box of rods on a shelf like most people do then 7014 will be stronger than 7018 because 7014 isn't effected by moisture in the air.
We are talking about structural work though. I wouldn't weld any steering components with improperly stored 7018 rod but if you're just welding your lawn mower together and have an open box of 7018 laying around then I think you'll be safe.