Tips for a non noob, but new whm ?

[CalvatE]

SCH has Lustrate, which scales with HP (heals 20% of max) and is spammable and instant-cast. The downside is that it requires Aetherflow stacks so it may not always be available.

When you take away Lustrate though, a SCH does actively top off a tank less.
Not to be mistaken to the fact that a SCH heals better, just that since half of the heal a SCH does is mitigation, it's not something you actively see in your HP bar - to of which, it doesn't 'top' a tank off.

A lot of people agree that the two healer's in this game are pretty well balanced. Heck even for end dungeons. People want SCH for AK (Fairy heal autopilot while you DPS), and WHM for WP (Holy spam). Bahamut's Coil? Run both!

OP I'd say just save up the myths, keep playing both classes - and then determine which one you'll find is funner.
Both of them are as viable as the next, regardless the dungeon. Some dungeons have preferences, some don't. Like I mentioned above, SCH favors AK, WHM for WP, but that doesn't mean you can't take one or the other at all.
I'd recommend trying all of the primals honestly, especially Garuda and Titan HM. Those are good tests of real battles to see what it's like to be a healer - providing your team isn't over geared.
End game dungeons are something anyone can do playing with their feet so don't judge your class based on these.

When you've decided, take on BC.