A huge difference. At 9,000rpm the vibrations induced by even a slightly out of balance prop will put undue strain and cause premature wear on the bearings as well as transmit undesirable vibration through the craft to the gimbal.
Out of my original four props (I haven't opened the others yet), three needed to be balanced. Not much, but ever so slightly. I used a fine steel wool to remove the access, little by little.
They fit. It's a tight fit, but you only need to insert part-way to get a good balance. I use the DuBro and it works perfectly. Checked all my 1345s quick release props, and found they are all balanced.