For end game content, like Trials, Wardens are really great to have around, if combined with a templar. They synergize really well. The NB Healer brings more damage to the table and is more suited for Dungeons and vDSA, but still really fun to play. They both have their unique thing to add to the table. So they both have their strengths. NBs can do Trial healing too but they don't add as much support as a Warden would do. And same, a Warden healer can deal damage too but a NB can heal more while doing damage.
On paper and in application, nb and warden are both on equal level dor trial healing. Nb has a slightly steeper learning curve for healing but they are both great.
All of the 5 healers' innate healing tools are weighted against the restoration staff differently. In some cases they lean more towards the resto staff skills directly where as with others, there are direct anolgues of resto staff skills which can be more beneficial and thus those classes lean less on the resto staff. I only say this because of your thread title. There is a demographic on these forums and in game that think non templar and non warden healers are "resto staff healers" and thus should not be taken serious. This is laughably false of course.
I'm going to mess this whole thread up and say nightblade. The real issue though is how quickly you want to get there. Magblade healer will take a significantly higher amount of skills to heal, but the beauty is that while you heal, you are dishing out tons of damage. You effectively make your dungeon group 3 DPS and a tank.
For tons of fun a heavy armor magblade healer using mystic guard on the tank effectively becomes a healer, DPS and off tank.
I definitely love my NB healer. Very fun class & role combo to play with plenty of ways to build it.
It also tends to be a conversation starter in random PUGs who may not be familiar with NB healing, if you are into the social aspect of the game at all.
I love my magblade. If I am farming a set, I can switch to a resto staff and apply dots/heal to get fast queues, and then swap back to dps for everything else (for me personally, I don't enjoy healing but NBs are very competent healers). I think I often shock people with the dps output a magblade is capable of in dungeons. I really enjoy it.