Most people would not notice but if you look at the blades of grass, sharp blades cut it cleaner, blunt blares tear/feather the ends. Also mower doesn't have to work as hard with sharp blades either.
I once got into an argument with a bloke selling "Made in China" replacement blades for Rover. I bought some to see what they were like. The first thing I noticed was they were extremely blunt compared to genuine blades. I sent him a message and he scoffed at any suggestion that blades have to be sharp. He argued black and blue that it makes no difference because blades go blunt almost as soon as you start cutting due to sand and grit flying up off the ground etc. Anyway I tried the blades and found lots of grass stalks feathered, uncut,and left standing. I gave his blades a sharpen and the difference was plain to see. There was nothing wrong with his blades. I've been using them for over 12 months now and they are wearing no faster than genuine blades. Quality is very good. Only problem is they come blunt from the factory and so you have to give them a sharpen with the file prior to using them. Obviously the problem was with the product not being "finished off". I guess you only get what you pay for, and stuff coming from China can be hit and miss, depending on the factory and the level of "quality control".
