I also recently upgraded from a Scorpion X1B with an external speaker. Went with the X24, but considered the Hellcat Pro.
The X24 has plenty of volume, much louder than the Scorpion. I rarely turn it all the way up, even when I am using locator calls. Although I miss the portability of the Scorpion, no regrets on the X24. The remote range and features are way better. The battery pack is nice and holds a charge a lot longer than the Scorpion. Sounds are easier to download and are much clearer/realistic. (Guessing because of the tweeter and higher resolution sound files). The ability to download sounds from MFK are a bonus.
As I stated earlier, the only thing I miss is the portability of the Scorpion. The Scorpion fits in my fanny pack and I often carry it with me without the external speaker. It is nice to have while small game hunting or if random opportunities present themselves. For that reason, I am keeping my Scorpion as a backup, and for those situations.