He pretty easily reached the level of his master Komaki, learning his combat style which fuses several styles into one.
He learns 2 separate combat style almost entirely only through seeing them in action once. One style is a combo of wrestling styles and one is something similar to kickboxing.
Kiryu is superior to Majima in every way and Majima has been able to go from being a lower rung yakuza to fighting the strongest assassin in asia - Lao Gui. He beat him after sustaining several injuries, fighting a guy on his level and then having to deal with Gui who was a master of several weapons and used a gun in his fight. This level up happened in the span of like a few days and Kiryu has surpassed Majima by leagues since then.
"Throughout the span of the first No More Heroes Travis went from
being far weaker than his master Thunder Ryu to surpassing him,
defeating Speed Buster when he couldn't, then even stronger foes. Can instantly learn wrestling moves just from watching VHS tapes of wrestling matches"
"Became the strongest assassin in America despite, by the beginning of the game, his skills mostly coming from pro wrestling training and his only knowledge of sword fighting coming from
online correspondences and self-training, though even then his work as an assassin
was barely a challenge to him"
Kiryu has defeated countless professional assassins, took out entire CIA-esque team armed to the teeth with guns and rocket launchers (team as in collectively like 40-50 people), defeated an actual CIA assassin team, beat Andre Richardson who not only had rapid fire guns but was a mass terrorist who infiltrated the CIA and was undetected for years. Kiryu also took out Joji, who was an extremely high tier assassin both in japan and america.
Kiryu has mastered unconventional weapons from other countries by fighting their user once.
He has blocked point blank uzi rapid fire with his bare hands.
His agent style has him use lassos and crazy weapon like explosive cigarettes to throw his opponents off guard.
Even though this is just first game Travis I feel like it should be obvious that "defeated countless professional assassins" applies to the guy whose entire thing is killing professional assassins too (there's even a mission where you do fight the military, although honestly "he was undetected for years" is like, completely unrelated to combat skill), he's killed 100 opponents in a single bout himself. Fair enough on the usage of really bizarre weaponry but "lassos and explosives" isn't that out there, basically every boss in NMH one-ups the previous one in weirdness and by the end he's fighting literal superheroes and wizards and by the time of the sequel he's having mecha fights and throwing hands with Jason Voorhees, spy gadgets aren't really something he can't adapt to. Travis is also just generally durable and resilient enough (read: he eats shit really often) to be able to afford himself to take a few big hits without really struggling in the long run.
Upscaling is also important here. Kiryu took that 0.3 ton feat directly and took basically no damage and that was in Yakuza 1. He has gotten stronger and continuously grown more and more skilled, not to mention the fact that Gaiden Kiryu's combat style has been effectively perfected compared to previous games.
He's still inferior to Travis in AP no matter what (especially because Henry, who Travis is equal to,
also took the 0.6 tons explosion without any damage), and Travis has a lightsaber that chops even comparable people apart like it's nothing.
Kiryu has his Extreme heat mode which boosts all of his stats including a huge boost to his speed and a nigh-unbreakable defense.
With heat actions he has shown speed great enough to speed blitz opponents.
I would ask for scans of that, but either way Travis can straight up
slow down time and 100% just blitz him back. He also has amps of his own, though admittedly the way in which those work is a bit nebulous.
Finally there are the weapons which include swords, nun chucks, poles and far far more. He also has guns with infinite ammo, shotguns, a naval cannon, grenades, rifles and more. He shoots precisely enough to shoot down helicopter pilots from a moving car, shoot down rockets from rocket launchers flying at him from said helicopter in said moving car and more. He is genuinely insane when it comes to weapon mastery.
Guns are basically useless against Travis, doesn't really matter how good his aim is.
Overall, Kiryu may not go full instinct based combat but he has enough skill to make up for it and enough weapons to cause major trouble for anyone daring enough to fight him. He also has tons of health items which give him massive boosts in power and stamina. My vote goes for him.
Healing items are nice but Travis is gonna be chopping his limbs off or at least hacking away flesh if he gets a good hit in, can't heal from that, meanwhile Travis does straight-up have regeneration. Arguing stamina is also not really a good avenue given Travis' feats are arguably superior.