Depends on what you like, melee or caster.
With Feral, you can dual spec as tank and have very short queues. Gear wise they are the same with very little differences. You have less downtime, but aren't that strong in AoE. If you skip Nurturing Instinct, you will have weak heals that can become a problem when you need to heal yourself when you are 80+.
With Balance, you can dual spec as healer. They also have similar gear, but Resto has a stronger focus on Spirit. There also appears to be less quest reward gear for Balance. You'll have to stop and drink more often. The Eclipse mechanic does take some time to get used to. You also get Starfall, which is great for AoE farming.
Overall, I prefer Feral over Balance for leveling.