I'm voting for Tatsumaki.
If Boros stops attacking for a single moment, its wraps for him, as Tatsumaki would instantly one-shot him as she has to literally every opponent she's fought when she had a chance. He can't deal any significant damage to her with anything excluding Collapsing Star Roaring Cannon, which I'll get into later.
Assuming Armored Boros even is Rel+ (considering it's only granted to him through a possibly rating), he would have absolutely no reason to go to his Released state, let alone Meteoric Burst, which is his where his main wincon, BFR, comes from. This is due to Boros not needed the speed amps from his two forms to have the advantage in that stat over Tatsumaki.
Assuming Boros does instantly go into his Released form, another possible wincon people have brought up is the heat from his blasts that were stated to be
able to vaporize human bones (
1500°C), and we even see it vaporizing his ship, which should be at least comparable to steel (
2862°C), and although these are both impressive, we see Rover doing similar things,
vaporizing Showerhead and Supermouse. Shower Heads are usually made of either Solid Brass (
2600ºC) or Stainless Steel (
2862°C), meaning that Rover's heat is at least as hot as Released Boros'. What makes this important is that we see Garou adapt to be able to
resist the heat from Rover's blast and we know that Orochi's heat is superior to Rover's due to
Gyoro Gyoro knowing that Garou could withstand Rover's heat, but being
surprised that he could withstand Orochi's. Gyoro Gyoro's barriers were able to completely block out Orochi's heat without issue. We know that Psykos' TK should be at least comparable to Gyoro Gyoro, and we know that Serum Psykos' TK is superior to Regular Psykos'. Psykorocho's TK > Serum Psykos' TK. Tatsumaki's TK is superior to even that.
Tatsumaki's TK > Psykorochi's TK > Serum Psykos' TK > Psykos' TK >~ Gyoro Gyoro TK > Orochi Heat > Rover Heat ~ Released Boros' heat.
Therefore, Tatsumaki should have no issue dealing with Released Boros' heat.
Though assuming that Boros immediately jumps to Meteoric Burst, which is highly unlikely considering how it is his final form that he never used before prior to his fight with Saitama due to him outright stating that
no one has fought evenly with his Released From, with when applying logic, this means that he has had no reason to use Meteoric Burst in a fight before then, as he beat everyone with his Released Form, he would just start out with BFR and beat Tatsumaki.
tl;dr, Tatsumaki resists all of Boros' attacks including all of his heat-based attacks. Tatsumaki is much more likely to one-shot Boros before he even gets to Meteoric Burst, as it takes him a while to transform, and he's never used it once before his fight with Saitama.
Tatsumaki wins 9 times out of 10. Not really a difficult fight.