Both have their merits, so I propose a wild and crazy scheme. Watch the 1999 anime and the OVA movies to see a more detailed view of the first arcs. Then pick up the Hunter X Hunter 2011 anime on episode 76 to start the Chimera Arc, a 61-episode Arc that is my favorite inclusion in the series. However, suppose you were to pick one. In that case, the 2011 anime is the better adaptation without question due to a cleaner animation style.