Here's something less controversial

It's more like 2018. You never heard trap on the mainstream charts in 2012. You did hear it in 2015, Trap Queen was like the number 2 song of 2015. And yeah the style of trap was different from 2018 but still you had newer musical trends in 2015 that 2012 is not part of. Having said that, 2012, 2015, and 2018 are all different eras so 2015 isn't the same as either 2012 nor 2018 but if I had to choose which is closer then it would be 2018.

Yeah, I'd say 2015 is closer to 2018.
2018 was basically Drake's year, and in 2015 he released "Hotline Bling" which very obviously influenced his later stuff including his '18 material.

2018, easily. 2012 and 2015 are pretty different culturally, whereas 2015 and 2018 have noticeable differences but are definitely a lot more related.

2018 without a doubt.

Pop music is completely different from 2012, no more Electropop except Chris Brown's 5 more hours. Pop music is more minimalistic and semi-trap, Hotline Bling sounds very similar to God's Plan by Drake. You also had newcomers like The Weeknd, nothing Electropop like 2012, purely R&B or Trap. Selena Gomez' Good For You is with ASAP Rocky, and it has Trap beats as well, completely different from her 2013 Come and get it, and sounds closer to her 2017 album despite sounding very different. I also forgot to mention Same Old Love, has the same tone as Wolves. Rihanna is in her rebel phase at this point with BBHMM. Justin Bieber without a doubt has changed, from As Long As You Love Me, to What Do You Mean. He also had songs in 2017-18 with DJ Khaled, and his 2015 album is kinda close to sounding like it. Shawn Mendes, while his 2015 and 2016 songs sound a little different from 2017-19, is also another example here, Stitches and In My Blood are both core 2010s pop-rock. 20% 2012, 80% 2018.

EDM is relatively similar in some ways, the aggressive synths are somewhat relevant still in 2015 thanks to Zedd and Martin Garrix, but it's mostly replaced by watered down sounds thanks to Jack U and Skrillex's Where Are You Now, Chainsmoker's Roses, Calvin's How Deep Is Your Love, and DJ Snake's Lean On. 70% 2018, 30% 2012.

Lastly, Trap music. While it's not as big as in 2016-2018, it's already mainstream at this point. Yes, it sounds a little different, but 2012 barely had any Trap. Drake sounds completely different from his 2011 album as hes mostly Trap with his 2015 one, and he hasnt changed his style since then. First-Wave mumble rappers like Rae Sremmurd, Rich Homie Quan, Fetty Wap, and a lot of other rappers inspired Second-Wave rappers like Lil Pump, Lil Uzi Vert, Lil Yatchy, Desiigner, etc. Watch Me Whip/Nae-Nae was one of the biggest songs for 2015. 90% 2018, 10% 2012.

Short answer: Leans closer to 2018.

I also forgot to mention that Dubstep in 2015 was no longer popular, replaced by Trap Nation sounds or NoCopyRightSounds on YouTube.

Wow, I'm honestly surprised at the results.

2015 is definitely more like 2012. Not only was the hip-hop very similar (Kendrick Lamar had hit albums in both of those years), but 2012 and 2015 were more upbeat and millennial oriented compared to 2018. Songs like "Can't Feel My Face", "Shut Up and Dance", and "679" are some songs that have more in common with the upbeatness of 2012 than the downbeatness of 2018.

2018 was a lot more downbeat, with songs like "SAD!" and "This is America" dominating the billboard charts.

Wow, I'm honestly surprised at the results.

2015 is definitely more like 2012. Not only was the hip-hop very similar (Kendrick Lamar had hit albums in both of those years), but 2012 and 2015 were more upbeat and millennial oriented compared to 2018. Songs like "Can't Feel My Face", "Shut Up and Dance", and "679" are some songs that have more in common with the upbeatness of 2012 than the downbeatness of 2018.

2018 was a lot more downbeat, with songs like "SAD!" and "This is America" dominating the billboard charts.

I mean, this was the year where Halsey, Travis Scott, and Post Malone got popular. Songs like Hotline Bling and Sorry have a sound that didn’t exist in 2012.

Also, dancehall became very popular in Mid 2015 thanks to DJ Snake, which was soon to be followed by Justin Bieber and Drake! I dont recall hearing any dancehall music in 2012, while 2018 still had a decent amount of dancehall

Also, dancehall became very popular in Mid 2015 thanks to DJ Snake, which was soon to be followed by Justin Bieber and Drake! I dont recall hearing any dancehall music in 2012, while 2018 still had a decent amount of dancehall

DJ Snake isn't dancehall though, isn't he EDM? Same as Justin Bieber's 2015 album, it's just EDM (but the song Sorry is dancehall though). I think dancehall died in 2017 actually, Ed Sheeran's Shape of You was the last one sounding like that.. It was an early late 2010s trend if that makes sense. Dancehall was songs like Sia's Cheap Thrills, it's kind of like tropical EDM. I always think of dancehall being exclusively a 2016 thing

DJ Snake isn't dancehall though, isn't he EDM? Same as Justin Bieber's 2015 album, it's just EDM (but the song Sorry is dancehall though). I think dancehall died in 2017 actually, Ed Sheeran's Shape of You was the last one sounding like that.. It was an early late 2010s trend if that makes sense. Dancehall was songs like Sia's Cheap Thrills, it's kind of like tropical EDM. I always think of dancehall being exclusively a 2016 thing
Well, a lot of DJ Snake's songs are Dancehall EDM, Id say. The cool thing about EDM is that in comes in many different forms, from the Rock-like New Wave to High NRG, Tropical House, Trap EDM, Electropop, etc. The last popular dancehall song I heard was from 2019 though, I dont care by Ed Sheeran and Justin Bieber sounds pretty adjacent to Shape of you