at this level bracket you have three options: Arathi Highlands, the Northern Stranglethorn and the stonetalon mountains. Two of these (Arathi and Stranglethorn) are on the continent of Eastern Kingdoms, while stonetalon turned off by itself in Kalimdor. That’s something to consider if you are your choice, but I concentrate especially on seeking enjoyability and ease of progression here.
ARATHI Highlands: this zone is practically as this before the cataclysm apart from a few minor functional changes. That makes the searching here is pretty vanilla (and a bit disconnected from the rest of the world), but it’s a good area for collecting. It feels a bit like the land that time forgot, which means it would be a good area to get rid once the expansion comes from (only you, ore, and a bunch of raptors!). However, there is only one flight path for each faction, so it’s not necessarily the best for convenience.
Northern Stranglethorn: this is the top half of what used to be only Stranglethorn, but the zone is now shared by a huge waterfall/whirlpool. Accordingly, the searching in this zone is completely new and very nice. There are also two routes here for both factions, which makes things a bit faster. However, there are the facelift and easy progression to the Cape of Stranglethorn sure visited a zone when the expansion is released.
stonetalon mountains: this zone also saw massive changes with the cataclysm, which means that the quests are fresh and fun. Quests are some strong role-playing elements around the Horde and Alliance battles for resources and territory. Since the zone of course is quite mountainous, there are five routes for each faction here, which makes getting around much more efficient. And not surprising that the zone is heavy on the mining industry. As Stranglethorn, this place could see a lot of activity/action (if you’re excited about PVP are), so it will probably not be the best for fast leveling.
all in all, I’m going to go with stonetalon mountains. A lot of good attention received it in the last expansion, with many citing it as their favorite zone for redistribution. As much as I say Arathi Highlands would want to, most people have probably a monk redistribution via Arathi countless times. Do the same quests, eight, ten times a huge slog, especially when some of them still have not been properly updated to reflect changes to the rest of Azeroth. If you are looking for search in solitude, however, the clear choice would Arathi Highlands.