If you're used to the Hellcat, the Pro version gives you slightly more capacity and a bit more velocity while maintaining the same ease of concealment. It would be pretty natural to have a standard Hellcat as a backup to the hellcat pro holster, either in a pocket or ankle holster, with the Pro inside the waistband. It's a similar setup as a Glock G26 backing up a G19 – right down to sharing magazines (the Hellcat can use Hellcat Pro magazines, but not the reverse).
If you're trying to decide between the two, the best advice we can offer is to see if you can try both out side-by-side. Whether the Hellcat Pro provides more of an advantage in shootability over the concealability of the standard Hellcat is up to the individual shooter; how either carries will vary similarly. In either case, it's a thoroughly modern pistol design with a robust and growing aftermarket—lots of choices, which is good.