See the Rune Priest. Some differences appear at later levels, but they are almost the same class at level 10. Instead of a big stick, the Zealot has a dagger before him along with poor Yorick.
Zealots seem rare and/or difficult to kill. They are the only class for which my Engineer does not have “kill 25” completed. I assume the other options win out. If you want a healer, you can be a Disciple of Khaine (redefining overpowered) or a Shaman (great flavor, green death ray). If you want to play Chaos, you can summon demons from your hoverboard, turn your arm into blades and tentacles while shouting “Tetsuo!” or play the only armored knight-looking class in the game. “Slavering cultist” is less cool, as is the special mechanic “a buff.” They do have the advantage of being nearly invisible on the battlefield except for the characteristic slouch and dagger slash.
As a healer, the experience differs because the number of tanks does. Destruction has too many tanks while Order has too many ranged DPS. My Rune Priest ran a scenario in which the allied team was all Bright Wizards and Witch Hunters (one of them above level 5). My Chosen ran a scenario in which his team was five other meleers. These are only slightly unusual. As a healer, I prefer teammates who can survive the few seconds I need to notice damage, switch targets, and cast a spell. The Bright Wizard is blowing himself up even before two Marauders start mutilating him. The slavering cultist likes hiding behind meat shields.