What's the advantage of the Smart over the Harmony Ultimate?
Ok, so my understanding of the Harmony Ultimate is that it's the touch screen version of the Harmony Smart Control...
Both come with a RF controlled "hub" but the Ultimate is able to add more devices (natively - because there's the usual harmony work around on the "Smart" version) and the Ultimate has a touch screen.
If you've got a Harmony Ultimate that looks like this:
Then I'm led to believe that if you DON'T have the hub, you should be able to buy it separately and do everything the Harmony Smart Control can do.
HOWEVER - I also think it's possible there are older Harmony Ultimates that you're referring to, that maybe doesn't work with the Hub. In which case updating to the new Harmony Ultimate, or Harmony Smart Control, might be a good idea.
At the centre of them both is the RF controlled Hub with built in IR blaster (and optional external one) that means your remote doesn't need line of sight to control your TV / AV devices.
I take advantage of this by putting all my AV in a cupboard.
Additionally, personal preference means I prefer the simpler Smart Control remote because it DOESN'T have a touch screen (I hate touch screens on remotes) and in turn, this also means it doesn't have a charging cradle!
Also, as a long time Harmony user, I much prefer the new range of Hub based remotes because they're much more responsive - in two ways.
First, when you press a single button no longer is there a 0.5s delay when trying to turn the volume up one click at a time.
Secondly because your remote no longer requires line of sight "activities" (that do a sequences of button presses) preform perfectly 100% of the time - and you don't have to hold out the remote out at arms length for 15 seconds while it turns everything on.
Lastly, the Hub can be controlled from the Harmony smart phone app - meaning you don't even need to use the remote. Not something I use (again, I hate touch screens for remote) but some people find appealing.