I looked this up because I wanted to know for sure. So obviously I have only preference to fall on. I giggle at some of the comments on the redundant sound of pleaded... Like runned-ed. Everyone knows it's ranned-ed :)

Indeed plea is the root of plead, but plea is a noun, and cannot be conjugated. So I can't really 'hear' the redundancy of pleaded unless it's pronounced pled-ed, because plead (pleed) is not plea-ed. Confused yet.
I'm not saying one is right and the other is wrong, I just can't find a straight answer. It's all a matter of opinion

Sure read and read, lead and led, bleed and bled...
What about need and ned, heed and hed, seed and sed? Oh wait...