Hi everyone I'm Jack Red, around my early teenage years I got into Yu Yu Hakusho. Still one of my favorite animes to this day. I recently got into his more popular work Hunter x Hunter. Which was very different in comparison at the same time being one of the best stories I ever heard. Hunter x Hunter originally had one anime to be followed in Japan by a OVA series.
A couple years later, a new anime based on the manga comes. I would say just like JoJo's Bizarre Adventure the similarities & differences makes it difficult for a comparison. I truly respected the author of those stories. Hunter x Hunter manga is still running despite some long breaks it had in the past.
Both versions of Hunter x Hunter has a lot of the same characters present. Some had a more notable role in the original version. Mostly there isn't a lot of key differences in what they do. However most of their appearances changed either a little or for many characters a lot. Both of them has a great usage of characters for it's time.
Hell it should be since the manga is one of the most popular in the world. Hunter x Hunter 2011 simply has more characters including a lot of chimera ants. Which is difficult to compete against in the long run. I should mention Hunter x Hunter 1999 OVA finishes off a story arc before fully doing Greed Island arc.
But they haven't been officially dubbed in another language. Hunter x Hunter 2011 covers all of that. A lot of interesting characters doesn't appear in the original version. The main characters themselves are respectively portrayed well. Although Gon's hair in the 2011 version is more accurate to the manga.
Both animes starts from the beginning of the manga. 1999 version technically left off with Yorknew City arc not finished. The OVA starts from that up till the end of Greed Island arc. 2011 version continues into Chimera Ant arc and 13th Hunter Chairman Election arc. I should mention like Fullmetal Alchemist: Brotherhood, 2011 version does quickly speed through a lot of story.
Although it doesn't felt rushed at all. Chimera Ant arc is the longest story arc in that version. From Chimera Ant arc to the end is going slower than usual. But it is barely notable after a while. The story in both versions is faithful to the manga. There is some filler stuff in the original 1999 version that alters the direction of story to a degree.
Let's be honest you are getting a truly great story. But you will get much more of it in 2011 version. Also the violence is more mirroring it's manga counterpart than 1999 version. They chose to tone some parts down in that version otherwise it wouldn't be allowed to air. It wasn't actually that violent in matter like Elfen Lied or Hellsing Ultimate.
There was a big time difference between both anime versions. I would say both of them had great animation at the time. 1999 version is similar to many animes of it's time. 2011 version is unusual in it's quality. Although it is very great animation. Hunter x Hunter covers a lot of terrible moments. More faithfully done in 2011 version.
I would say in comparison 1999 version can be considered a little choppy. All the characters are done well while those same characters are really done well in 2011 version. They allowed much more gory moments in 2011 version displaying some amazing talent. I don't want people to think I don't like 1999 version.
I honestly like both of them with the animation not quite on level with 1999 version's OVA series. You can tell they were rushing them out but it isn't horribly done either like the new version of Berserk. You can clearly see 2011 version did take time covering what already has been adapted with 1999 version. At the same time covering newer arcs not animated before.
3-0 Hunter x Hunter 2011 version is the better anime. They may have sped through all the stuff 1999 version including it's OVAs covered. Plus adding two story arcs that are both great in their own right. The overall animation of 2011 version is widely superior. If you love the characters then 2011 version will give you more reason to do so.