Jackson had a pretty good record in the Shenandoah<snip> Given his record of quarrels with his subordinates before, during, and after - I would be extremely leery of giving him the AoT. Someone with Jackson's lack of people skills would not be someone who would work well with the exceptionally terrible AoT generals and their attitudes. Whether he would be right to - say - arrest Polk isn't the point, Jackson would have no better luck than Bragg at making it work harmoniously.
Add in the responsibility of independent command on a large scale (50,000+ men instead of less than half that ever before), and it would be chancy. Not to say anyone promoted from lieutenant general is obviously better, but that's not the point.
Jackson's biggest problem in command was that he established for his commanders the ideal that you did exactly what you were told to do and not one step further, or God help you. In some ways, there was just a little bit of Custer in the man in this regard.
This command style remained with his units long after his death, which really bit the AoNV in the ass on the First Day of Gettysburg, the corresponding actions of Ewell's Corps through the battle, and at North Anna River in 1864.
Longstreet in the West failed dismally against Burnside, also wound up unable to work with his subordinates (McLaws, specifically) and his favoritism of Jenkins over Law also caused friction. Again, not something you want in someone commanding the Confederacy's biggest collection of dysfunctional and arrogant insubordinate buttheads.
Horrendous terrain, a single line of approach, impossible logistics, atrocious weather, and Burnside having the month of his life.
Forrest was a prick, not a butthead. And Cleburne was good.
His performance as a subordinate was generally first rate, and his tactics and organizational skills were good. But as with Jackson, what he could do with a corps doesn't necessarily mean he's prepared for an army.
I haven't heard of him having problems with his colleagues in the AoT up to the Battle of Chickamauga, save for Bragg. If he could get along with them at the same level of command, would it be so difficult as their commander? And could he fire Polk himself?
If I had to pick on pain of my dog being shot or Beauregard given command , I'd lean slightly to Longstreet if only because Jackson is likely to inspire his subordinates to act like they did to Bragg - does anyone see Jackson handling the case of Asa Lewis any differently, to pick an example of Bragg being in the right (by military law, at least) but still leading to a feud?
Given the AoT's problems, neither man would fill me with confidence.
Actually, if wiki has it right, Bragg was a murderer.

Asa Lewis' enlistment ran out, so he couldn't be considered a deserter. Especially of a state that was not officially in the CSA. But yeah, I'd see Jackson doing the same.
I agree about having poor confidence in both men. Consider what would have happened on the Third Day of Gettysburg had Lee listened to Longstreet and moved his corps around the Federal left flank?

Not good. A rare case of my supporting Lee over Longstreet at Gettysburg.
And there's always Beauregard.
For many of the reasons Elfwine already stated, neither is a good choice but if forced I'd go with Longstreet.
Placing a loony like Jackson in charge of the collection of egotistical assclowns who comprised the Army of Tennessee's upper officer ranks would quickly make people miss Braxton Bragg.
Even 19th century Southrons in a revivalist age thought Jackson ran the gamut from slightly weird to totally nuts.
Choosing between the two, I'd go with Longstreet. Putting Jackson in charge of the Arrmy of Tennessee would be like pouring gasoline on a bonfire to put it out. Looking at all of Lee's Corps commanders, Richard Anderson, Wade Hampton, or Richard Ewell seem to have potential.
Anderson only had one outstanding moment on his whole career, his race for Spotsylvania Courthouse. That's pretty much it. Lee made the right choice when near the very end he fired Anderson and Pickett from the AoNV.
Wade Hampton was good, but you can't put a cavalry commander in charge of an ACW army. When Davis appointed Forrest to command of the surviving CSA forces after the Battle of Nashville, he didn't do it just because Forrest had the best record in the CSA Army in the Deep South. He did so because cavalry was most of what was left in that region for the Confederates.
Richard Ewell as a corps commander was a man who seemed to lose ability each time he got shot. And he relied far too much on the advice of the overly-aggressive Jubal Early.
Jackson was a brilliant (if overrated) commander, but he assuredly did not have the personality to handle the difficult personalities that made up the Army of Tennessee high command. Longstreet was not good as an independent commander, but would have done better than Jackson did.
Fact of the matter is that so long as Leonidas Polk is a corps commander, no one is going to have an easy time of it as commander of the Army of Tennessee.
Which comes back to the question: Will either Jackson or Longstreet have the power to fire Polk? I'm pretty sure Davis would interfere in that.
I'll go the other way and argue in favor of Jackson (although I agree that neither choice is likely to be particularly successful).
Jackson, unlike Longstreet, does have a prior record of success in independent command.
So, I vote the slim chance of success for Jackson over the almost non-existent chance of success for Longstreet. But, as many people have argued, the underlying problems with the Army of the Tennessee are much bigger than just which general gets the top seat.
I disagree. Depending on when it happens, if Longstreet takes over after Grant goes east, he might be able to exploit Sherman's less than expert tactical ability. Though Thomas and McPherson will still be there. OTOH, if Grant is still there...
Certainly Jackson's rep would help. But how much did Longstreet's rep (as a veteran of the AoNV) help him OTL in the Aot?
As for dealing with Davis, (1)
Where is this slim chance coming from? Yes, Jackson has a better record in independent command - but his prestige isn't going do a lick of good of good at making up for the fact his command style is going to be about as pleasant as a slap in the face. And with subordinates acting like that, any chance of his plans working - which in previous campaigns required his subordinates to be willing to go along with being essentially kept in the dark - disintegrates into nothingness. (2)
1) Especially Davis' tendency to micromanage the AoT in terms of the power to hire and fire.
2) See above about "shut up and do as you're told" & "similarities to Custer's command style with his immediate subordinates".
I don't want to Longstreet is a good choice - but I am missing how Jackson has any advantage at all in a situation where all his weaknesses are in play, (3) and those weaknesses are ones that are particularly well suited to aggravating the AoT's problems.
3) Another weakness that I haven't seen listed yet: More than any other ACW general (AFAIK) Jackson could not admit error and certainly not failure. Refusal to admit responsibility for defeat in battle and seeking to blame others is one thing. Common enough everywhere in the military.
Court-martialing your subordinates for COWARDICE
because YOU got the pants beat off of you

by a clearly inferior opponent is another.

The opponent a master swordsman fears the most is the worst swordsman. All too often, in chess, when a master unexpectedly loses to a neophyte, he cries "CHEATER!!" and kicks over the board.
When I think of that kind of egotistical personality being sent to rule over the roost of the AoT...
