Both options are viable and each with their own pros/cons. If you have 1+ Mage in your party and thus free Water and will be drinking anyway due to caster DPS then I don't see a downside to Paladin+Priest unless you really want to main a Warrior and/or are doing raid content with Crushing Blows.

Priest+Paladin gives 2 Rezzers, an off healer, more buffs (and thus a slight improvement to overall party survivability), good "oh shit" options, and Priest healing brings extra tools to the table (you can HoT, Shield, & AoE Heal in emergencies).

Paladin healers are by far the best single-target healers in the game and generally the most mana efficient and can be fine for parties as well but you do have less tools so generally Priests are a better recommendation for most boxers (note that I main a Paladin and prefer Paladins over Priests for myself).