How about take both ? 
It seems an anti mainstream idea.
But it should works, highest flat RR will applied.
And they have different duration time and perhaps different target too.
The advantages of taking Wind Devil - Raging Tempest as flat RR :
- we can save more devotion points
- can be as source of damage if we invest good enough points
- can be as CC too (Impaired Aim)
- more slot for bounding devo skills
- doesn’t need xp for lvl up, just put more skills to max level
In the other hand, Elemental Storm :
- we can save skill points and can spare more mastery skill points
- longer duration of RR
- reduce skill usage in the keyboard/mouse
- nice coverage area (no AI)
Sometimes it depends on the build and personal preferences.
There’s build ‘hunger’ for mastery skill points --> take Elemental Storm
If need on devo points --> take Raging Tempest
If someone doesn’t like too much skills on the keyboard button --> take Elemental Storm
And if the build is okay and can handle many active skills --> can take Raging Tempest
Here’s an example, in this build actually I can take both Elemental Storm and Wind Devil-Raging Tempest.
Elemental Storm bound to Storm Totem.
But if I did it, it will ‘delay’ my RMB skill.
Also like I said about preferences, I prefer less active skills on the keyboard 
I just like Elemental Storm than Wind Devil-Raging Tempest.
Elemental Storm bounding to Storm Totem is nice, reduced keyboard button pressed.