I have both the Wiki 84 and the Mana 90.
I use the Wiki for surfing because it has a shorter wider blade (so less to get in the way but good power when you need it).
The Mana I use for flat water and downwinding (so 12'6" and 14" boards). It has a longer narrower blade that allows you to really bury it and keep your paddle shaft vertical.
Have never used them the other way around as this just works. Most of the crew I've seen with these paddles use them the same way.
If I was only going to have one paddle I would stick with the Mana. I have both, the wiki is very blunt in comparison and not as stable. I repurposed it to flat water foil take-offs only. Mana 82 is powerful enough to cover most humans imo. You can't go wrong with it.