Between MTV or The WB, which network had a greater impact on teen/youth culture?

Are you kidding? MTV by a country mile. It’s drove youth and media culture for a solid 25 years.

MTV. MTV was worldwide, that other channel was US only.

MTV. And the WB isn’t even a close second.

MTV by an insane margin

As a teen in the early '00s, I honestly didn't know anyone who watched either back then. Adult Swim was the must-watch for that decade amongst my circles. But MTV for older generations.

I'm 34 so I was a kid in the 90s and a teenager in the mid-2000s. But I've never watched MTV, ever. My family didn't have cable when I was growing up, but I've watched a lot a lot a lot of TV from the early to mid 2000s mostly on DVDs and later on streaming, and no MTV shows have ever been on my radar. I don't remember kids at school talking about those shows. I've heard of Beavis and Butthead and Daria a little bit online but couldn't tell you anything about the real premise of either of those shows but I've never heard of The Real World. WB was a lot more accessible as network television and those shows were everywhere during that era.

The WB wasn’t even available everywhere in the US. I remember watching MTV in middle school but the WB/CW channel didn’t show up till after I was in college. I only knew of shows like Dawson’s Creek and Felicity from teen magazines. 

These answers may vary some. Because WB was offered through antenna tv and mtv was cable. I think, most would say mtv. It had such a significance on young adults that transcended into everyday life.

UPN “am I a joke to you?”

The WB didn't make it outside of the USA.

Let's remember that the WB debuted in the mid-90's, as MTV was still playing music videos. Today, MTV is on fumes, no music, the VMA's are now a dog & pony show. CW, which was the fusion of WB & UPN, is broadening its sports portfolio (NASCAR, NXT, NCAA, etc.), something MTV never did.

They say there are no stupid questions. They were wrong.

For Gen X, MTV was their babysitter while mom and dad were off doing whatever. It shaped that generation's youth culture. It shaped their fashion. It shaped their taste in music. It shaped what they wore. How they wore it. It drove Gen X to pick up a guitar or start rapping in a mic. For Millennials, WB shaped them. By the time they became the older teens and younger adults, MTV was dying. MTV shows like Headbanger's Ball, Yo MTV Raps and 120 Minutes were already cancelled or were airing sporadic. Meanwhile, Millennials were glued to their television watching the likes of Buffy, Gilmore Girls and Dawson's Creek. Not mention when WB became CW and the channel went more Arrowverse and Supernatural came along, stores like Hot Topic, which was a hang out for younger Gen Xer with their music leaning themes switched over to CW leaning themes and dropped their music identity. Millennials wore fewer and fewer bandshirts and more TV themed stuff.

MTV did and it isn't even close. They managed to massive disrupt the entire music industry, youth landscape and exerted their power in the 90s. They and the record industry began a push for Grunge, alot led to believe the top directors at MTV ordered it. Why we know it wasn't a gradual shift is because all the charting data is still available. So the 80s Hair Metal was still performing massively, charting in the top right at the time Grunge was getting pushed. A lot of Hair Metal acts charting no. 1 on MTV. A big example of this was Trixter. They had a blow up in the span of a brief few years, and were constantly hitting no. 1 on MTV in 1991. 1992 hits and they're instantly cut along with all other hair metal bands The first immediate casualty was Tuff. They got their video charting on Dial MTV at no. 3, right behind GNR and Metallica, you couldn't get bigger. The next week Smells Like Teen Spirit drops and Tuff was never heard from again. It was that fast. 14 weeks later Tuff would be dropped by their record label. There was still big demand for rock music, but hair metal was murdered instead of it being slow rolled. It's why some rock acts survived through. And you had Hair Metal adjacent media still pop off. Wayne's World movies, they wouldn't make sense to even continue producing. You wouldn't greenlight Air Heads if it was a natural decline. If you want another example of the craziness happening, look at Damn Yankees. They were a super group of musicians from other successful rock bands, they were paid $1 Million to not release their 3rd album. The label bought their contract out. Overnight Grunge and image of it took over and culled the existing music. MTV pushed it faster and sped up Grunge's ascent while killing off Hair Metal. That's the influence MTV had. And it continued for a long time until you get to the Ridiculousness era, just waning over time.