The standard Blackberry Storm charger shows its output 5V at 700mA, but the Droid charger shows 5V at 1000mA.
I am not an electrical person, but something tells me that they are different, even though the ends are the same. I charged my battery up with the storm charger initially, and have used the Incredible one ever since.
This might be a placebo effect, but I have noticed that the charge seems to be 'different' when using the two chargers. I noticed the charge doesn't seem to last as long after using the Storm charger, but ever since I used the Incredible one, it has been longer in usage. Then again, it could be beause the battery is getting broken in...