I feel I need to watch 2gether again just to compare it to everything I've seen since but the answer is definitely Bad Buddy IMO. As with loads of people 2gether was my first bl and I remember being obsessed for a short while as it was a different type of queer programming than I'm used to seeing (ie there wasn't a lot of stigma towards being gay in the series, and it wasn't the focal plot point), but it definitely falls short in a lot of ways. High five aside *cough cough* I feel like it decreased in intimacy and instead increased in bromance towards the end. Also the chemistry doesn't compare to other shows. No offence to Bright at all but I feel he didn't match Win in acting, so even though they looked great together sometimes I didn't feel the chemistry as much.
Bad Buddy on the other hand oozes chemistry. Ohm and Nanon compliment each other so well and their acting is SO natural. Their relationship progression actually feels realistic and it's exciting to watch. I didn't even like the series as much as everyone else did at the start, but they've managed to turn a normal story into something more imo. Plus the representation is great, there's no stereotypes, and the emotional scenes actually make me emotional. 2gether will always be a good beginner bl for me but it can't compete with Bad Buddy.
