Well considering I have never heard of Greta Van Fleet (sounds like someone that would be on Fox News), I am going to go with Kings of Leon. I looked up the other on allmusic and they are quite the critically reviled band.
Greta was a bit divisive when they first came out. Blurring lines of inspiration/ homage to ripoff. Positive way of looking was informally carrying on the torch. As time went on, they find their sound more, maybe??... wearing inspiration a bit less on their sleeves. They have a passionate fan base though. Don't have a dog in the fight. There were like a million of these articles back in the day. Some people still feel this way ... a 2020 article. https://metalheadzone.com/greta-van-fleet-star-reacts-to-led-zeppelin-rip-off-claims-one-again/
Sort of the point of this discussion. Both bands are considered hacks in certain circles. Haters gonna hate. I think they’re both fabulous.
The thing about these 2 bands is that it once again reinforces my belief that American music is still woefully behind British music. Even when the rare group breaks thru like a Sparks, they are still ignored in US because they aren’t “marketable” enough and of course, Sparks are bigger in England than in their own country that you would not be blamed for thinking that they are British.
Greta Van Fleet even if they are a wannabe Zeppelin Kings of Leon have always come off as boring to me.
I wanted to like Greta Van Fleet but I couldn’t get into it. I don’t think it’s trash, just not what I was looking for. There are a few Kings of Leon songs that I like so they win by default.