The irony is that if Lee had commanded in 1862, he might have taken Richmond. The war might have ended much sooner, before the Emancipation Proclamation. Slavery would have been weakened and it's hard to see Lincoln forcing the runaway slaves ("contraband of war") who had escaped to Federal lines to return to slavery, but the final end of slavery might have been much delayed.
I would agree, because Lincoln could not have imposed his will on Lee the way he was able to with McDowell.
In have always wondered what might have happened if Lincoln had met with leaders in Virginia instead of calling for the 75,000 volunteers. Virginia had voted down the session ordinance the first time. Without Virginia only the cotton states could have been counted on. The resulting conundrum would have been excruciating and the outcome uncertain, but different individuals could have emerged who are not part of history.