1999 had its own heart, it was not Hunter x Hunter as envisioned by Yoshihiro Togashi.
It was Hunter x Hunter as envisioned by Kazuhiro Furuhashi.
There are so many reasons why I do not like this adaptation of Hunter x Hunter.
But there are a few reasons I like it as an anime.
As an adaptation it is a failure, Furuhashi cannot resist the urge to create his own stories and messages, which are nothing like what is represented in the manga. The character personalities are poorly represented and in some cases completely altered. Furuhashi also changes Kurapika into the protagonist of the series as he was more interested in Kurapika then the other characters, which is why he rushed Heaven's Arena and utterly ruined the arc. He had no interest in Gon and Killua and treated them as secondary characters instead of protagonists. If you have ever seen the final script (an original ending he had planned) you would laugh, Furuhashi originally planned for Kurapika and Chrollo to both die, with Kurapika dying in Leorio's arms in a big dramatic full circle moment. Gon and Killua were then magically approached by Ging and that would have been the end. Thankfully that was not the case and the script was never used.
As an anime it is not that bad though. It has a decent OST with some stand-out tracks, but also has some very bad ones as well. The animation hasn't stood the test of time but it undoubtedly has an atmosphere about it. Furuhashi fleshed out some characters with non-canon filler but it did add more personality to some of them. I also must say the York New arc was quite compelling in this series but was not a good adaptation of that portion. If you like Kurapika, which I do, you will enjoy this series as he is effectively made into the main character. I don't mind it as he is an intriguing character. There is a number of inconsistencies in the series but all in all, its not a bad anime, its far from great though.
I think that the 2011 anime is better than 1999 as both an adaptation and as an anime series. It has more heart, it had great respect and affection for Togashi's vision and work overall, the animation is better, characterisation is better and music is better. All in all it trumps 1999 with ease.