No idea, two truly great, talented, veteran teams who were mentally unbeatable. Would have been an epic game. I feel both D's are good match-ups for the respective O's, and it's a wash that comes down to who do you prefer 2014 Brady and O vs 2004 D, or 2004 Brady and O vs 2014 D.
The interesting thing is the 2014 O actually appears a weaker version personnel wise in comparison to later era teams. Stork & Wendall on the line, Blount behind, Edelman, Dola, LaFell, Gronk, Vereen the receiving options. The 2004 D was absolutely loaded at all positions and is a good match-up vs the 2014 O on paper, especially in the trenches. But that 2014 O actually scored more points than all of the later 15/16/17/18 teams.
The 2014 D had a mix of veteran, prime and upcoming stars all over, and was deep. It had Revis and Browner, Wilfork, good Branch, Ch Jones, Ninko etc. 2014 in retrospect also really deep with most back-up players ending up as starters elsewhere in the NFL. 2004 was a good no.3 O with Dillon and early Brady with good weapons at all positions. That D is one that could potentially match up well.
Talent aside, those teams were so mentally tough. 2014 was the "We're onto Cincinnati" season, and there was something about that team mentally from then on that wouldn't be beaten, not against the Ravens or the Seahawks. 2004 also had that unbeatable swagger who were 3 years undefeated in the post-season were 18 undefeated in first part of that year.
My personal opinion is the 2016 team was the best and most balanced team of the whole era (especially if you add IR'd Gronk) and could potentially match up better against the 2004 and 2014 teams. 2016 were 14-2 only losing to the Bills with a one handed 3rd string QB, and the Seahawks on the goal line.
The D was n0.1 in PPG, it gave up less points than 2004! (250 to 260). It only gave up 20 points 5 times all year, and more than 25 points once (in one half of a SB), and no.3 O with multiple weapons at every position for Brady. They were also pissed after Brady's suspension.
I don't think either of 2004/14 could have come back from 28-3 like the 2016 team did.