Originally Posted by volosong

You will not be "bouncing" anymore. Or, your hips will be more level throughout the pedal stroke and not going up and down as you extend your leg fully. You'll be able to maintain power in your stroke all the way to the bottom of the pedal rotation. And, you won't have to flex your ankle, front to back, because your leg is not fully extended. It will just feel more comfortable.

It's not all the "bad" right now. You definitively don't want to go higher. You are wise to make small adjustments, (5 mm). Try it for awhile, then see how it feels. You can always go back up. Do you have cleated shoes and clips on the pedals? Or, are they just flat pedals?

As others have suggested, the best is to get a pro fit. It's a little expensive, (around $200), but well worth it if you are halfway serious about cycling. If you don't ride clipless or most of your rides are less than 20 miles, then the value of a pro fit is questionable.