type of charger has effect on battery life?

It seems that my battery has WAY more life when I charge it using the iPhone dock/USB wall plug that came with the phone...instead of other, third-party chargers.

I noticed that, when I put the iPhone in my iHome clock radio to charge overnight, the battery seems to fully charge, but power lasts barely a day with light usage. Same when using my non-apple iPod car charger.

Using the apple charger I was able to use my phone all weekend and barely drained half the battery.

Could this just be the battery coming into its own after several charge/deplete cycles...or does the type of charger make a difference? Are all fully-charged symbols created equal???