My vote would be for both healing spells and the ability to rest anywhere. Clerics should be for buffs, rez and heals, if I bring one along I should expect a melee party to have less downtime and tank better with buffs. If I don't bring a cleric then I'd want to fall back on buff/healing potions and the ability to rest anywhere to regain health.
Fair enough that rules and locations need to differ because it's not a AD&D. I've accepted I won't be able to see Icewind Dale, Menzoberranzan, Mithril Hall etc. On the plus side at least crenshinibon won't be surfacing again. But I don't see why we therefore need to have a radically different RPG forumla, with wizards that need to weightlift and clerics that can't heal.
Regarding resting to regain health, if I find some cubbyhole to rest in a cave system and I didn't pack any firewood I should still be able to rest there, bandage up and make with the magical healing poultices. Surely resting requires only being sleepy and not being chewed on by a bear. In fact I didn't want to light a fire in the cave system anyway as the smoke would give away my position, and I'd probably asphixiate.
Yes there should be an element of danger with resting and the party members needs to take watches. The risk should be based on the situation the party is in and be mitigated by locking doors, being undetected, finding a safe cubbyhole, carrying an expansible wizards tower, pocket plane, or having mark/recall spells to pop home for a nap. The only game I recall that prevented me resting iirc was Storm of Zehir and I thought it sucked that I couldn't rest in a sheltered cave I'd cleaned out, while being forced to go sleep out on a mountain with biting winds and monsters roaming about.