FMA is more consistent and the story less ambitious so it doesn't have plot holes. Low risk mid reward. And for that I understand how people crowned it the best battle Shonen on the internet, it delivers on its propositions but at the end of the day is a pretty common story.
HxH is not consistent in anything but its characters. Every arc might as well be a different anime, and people who liked one story might not like the next one because Togashi just follows his dreams and does what he wants, he isn't bound by any structure. First arc is too childish for some people, then we get superpowers out of nowhere in Heaven's Arena, then we get Death Note with fisticuffs that's actually a flawless masterpiece very reminiscent of Fma, he liked card games so he wrote Greed Island and finally he did the CA arc that's an animated philosophy book that gives the protagonism to recently introduced characters so it truly feels like a new anime if not for Gon and Killua. As I said, it's not consistent so it won't be for everyone, but it reaches highs FMA can't even see.
FMA peaks in the sadness department at the very beginning with the Chimera and Hughes. And it was done better in 2003,Brotherhood didn't really get me with Nina, she showed up for 5 minutes and had a giant death flag along her dog. Anyway those are FMA highs, they really hold no candles to Meruem and Komugi or Killuas breakdowns and Gon San or the Troupe grieving in York New..
So yeah, Hxh can get off track but then deliver the best moments you'll see in anime so it should be the new #1, sadly FMAs aesthetics look more mature so the mainstream won't ever rectify their vote.