Even if Garfiel can resist the heat, I'm still voting Bakugo
Garfiel starts out stronger, more skilled, and has Accelerated Development that makes him stronger over time
But at the end of the day Bakugo can fly. Bakugo just goes up and there's nothing Garfiel can do besides throw rocks and/or jump. Skill is nice but Bakugo doesn't often go in for close quarters, especially if he gets cooked the moment he tries to. If Garfiel gets close he doesn't have any options of putting Bakugo down before Bakugo realizes that him getting close is a REALLY bad idea, which he will realize quickly due to his intelligence and overall fighting style, so he just flies gg. Garfiel going up to chase him just causes him to get blasted back down to the ground and any rocks that he throws at Bakugo meet the same treatment, rinse and repeat till Bakugo blows his brains out
Howitzer Impact can 1 shot people on Bakugo's level due to the Serpenters feat as he wasn't able to touch them a single time and they were stronger and faster yet Howitzer KO'd them in a single hit, so landing a Cluster-boosted Howitzer is going to severely harm Garfiel without much backlash for Bakugo himself, and he can easily set one up due to his massive mobility advantage and Stun Grenade constantly catching Garfiel off guard. Yes Garfiel has instinctive reaction and can sense people with his Divine Protection but Bakugo is basically never on the ground so he can't sense him plus he's never fought fully blind before, not to mention even if he does dodge, Bakugo is much faster, much more mobile, and has massive AOE so Garfiel still gets caught no matter what he does
Accelerated Development simply isn't a problem for Bakugo since he starts out with a blitz level amp, isn't cocky enough to flaunt it, and can cause massive damage against Garfiel before he really gets going, and even after he gets going and can close the gap in speed and jump through the air, it still doesn't protect him from Bakugo pointing his hand in his general direction and blasting him back down to the ground. They both have similar stamina values although Garfiel's is better due to doing squats for a week straight, Bakugo is causing way way way more damage throughout the fight by just carpet bomb spamming everything while avoiding everything with Cluster speed amps and flight. Healing wouldn't quite work either since he's never used it in the midst of battle and he likely can't afford to be distracted while doing so, which, well, Bakugo is raining hellfire down on him the entire time so it will be extremely difficult for him to pull off the healing
Overall Garfiel just gets camped out