well I think mech has some serious advantages...but then again I think that Anakin would be resourceful enough and could last long enough to exploit a possible mechanical weakness in Mech Vader...I think that is mech vaders weakness that Luke never exploited in ROTJ cause he didnt want to kill his father didnt have time or foresight to use that weakness in ESB.....Look how easily Palps shorted out his suit in ROTJ.....Anakin was a resourceful jedi that I dont think would overlook that...but then again like you both stated Mech would be looking out for his former self trying to do that.....hmmm...plus mech would know exactly how to get under his skin.....but by doing so would he distract himself primarily thoughts of padme......etc....shoulda made this a poll so after winner was decided we could have a Nafarus story...lol...
Old age and treachery defeats youth and exuberance.
ROTS Anakin loses.
This would be the same as Hulk vs. Maestro; the older self can easily predict and anticipate every move their earlier counterpart will make. Not to mention Anakin is far too reckless and hot-headed while his older self is level-headed and calculating, plus he has far more experience and his fighting skills are far more refined and efficient.
Relevant examples of Anakin being overly hot-headed to the point you can take a fight as close as this and base your decision almost entirely off of that factor? If we're bringing up emotions factoring into a fight let's talk about what Anakin did to Dooku, and compare it to what Luke did to Vader.
Vader does have the edge of prior knowledge, I suppose, but then Anakin has better dueling feats.