before I get into this, both bakugou and yang are rated as having roughly the same stamina overall, meaning it is very difficult to tell who would run out of steam first.
So like I understand that Yang has higher AP than Bakugou's normal explosions and such, but Bakugou's Howitzer Impact let him beat a serious Todoroki, knocking him out in one blow and destroying a large portion of his super massive ice wall And Todoroki could withstand being close to that explosion caused by his quirk clashing with Midoriya's 100% Smash. On that note as well, Bakugou still took hits from someone clearly stronger than Yang (All Might who was restrained and stated to not be holding back during their fight) and was able to get up and continue fighting.
Also, Bakugou is still the smarter of the two in terms of being analytical. Like sure he is a hot head but he is able to at least formulate a strategy and be conservative with his power whereas Yang up to Volume 3 is more about rushing in and relying on her aura to win (As pointed out by her father).
Plus if he is ever feeling pressured, Bakugou can use his Stun Grenade move, which he used against both Tokoyami and All Might, meaning that he could open Yang up for a big attack or a bunch of smaller ones to help wear her down.
Like sure if Yang gets in a few hits, it'll be hard for Bakugou, no doubt about that. And if Yang's semblance goes off, then he'll have an even harder time and could simply straight up lose the match because of it. But given his superior intellect, his history of taking blows from clearly stronger foes, the fact that his Howitzer Impact has a large area of effect and high power, Stun grenade being useful for creating openings, and the fact that Bakugou could keep up against Twice, Toga and Compress all at once (Which would imply that he is capable of handling being on the defensive against people around his speed, which Yang is in this fight due to speed being equalized), I say Bakugou with high difficulty wins.
Reason for high difficulty is simply because Yang is stronger/more durable at base and even more so with her semblance and that Yang likely has slightly more reliable and more damaging long ranged attacks.