A few things to consider...
Not bashing KC at all, I loved the product and it got me into boxing.
But IS Boxer is the program to use for boxing, its exponentially better than everything else (HKN is probably the closest, lacking a few features and the graphical configuration interface).

Keyclone has broadcasting, where you push a key and everyone gets that key.
You can blacklist keys so when you push it, it is not broadcast.
Or you can whitelist a key, so only those are broadcast.
You can also have something on a given keybind for one toon but not for the others.

With IS Boxer, there are essentially two methods of broadcasting.
There is Repeater (which by default is both Keyboard and Mouse, but can be split into separate toggles), which is exactly like Broadcasting with Keyclone; and you can blacklist/whitelist keys to go with it...
But there are also Keymaps (which are groups of mapped keys).

Mapped Keys can have a variety of options, such as Window: Current, Window: Others without Current, Window: All, a pre-defined group (Action Target Group), specific character slot numbers, etc.
A major advantage of this, is having everyone with all spells and keybindings set the same, so you can one-box any of them with the same keys you already know.
But then use mapped keys, for your team... which will round-robin say your "6" key, when you launch as a team.
And which will send "4" to your current window only, without needing to have something on that key for your lead but not on that key for your slaves.

A repeater region is a phenomenal feature for healing.
It is a region, where broadcasting is enabled and sent to the client (slot) or group (Action Target Group) of your choice, but only while the mouse is in the region.
Combine this with Healbot, Vuhdo or Grid + GridCustom Layouts + Clique, and you have mouse based (click based) heals/buffs/cleanse/etc from any window to your healer without macros or keybinds.
I have a repeater region over the Jamba item bar, so when I click on the alchemist flask, they all click on it together.

My Death Knights have two "Send Next Click" mapped keys for Death and Decay.
In Warcraft they all have D&D on keybind Shift + A (so I could one-box any of them, and use the same keybind I'm used to while boxing).
Alt + A, does:
- Sends Shift A, to my Action Target Group of the DK's (four DK's in the group), but round-robin'd in the order they were invited to that group... so press 1 = DK 1, press 2 = DK 2.
- Sends Next Click to my DK ATG, which being the same group will be the same ordering.
A "Send Next Click", activates the mouse in the slave window, complete with a targeting circle that moves in real time, without any delay... and as soon as you click in the master window, the target (and only that window) receives the appropriate click, and then broadcasting is disabled.
Shift + A, does almost the same thing.
- All of the DK's receive the Next Click action at once, so the D&D is stacked in the same place (or very similar, subject to camera angle differences... which could be sync'd with a /setview type action), and the Paladin does Consecrate too.
The mouse broadcasting was the original main selling point, on what motivated me to switch to IS Boxer.

The instant swap from one window to another was another selling point.
At the time, there was basically one type of layout, whether across one screen (monitor) or several.
You had a main region and slave regions (picture in picture) or each with their own portion of the screen/screens.
Now there are layered options too, which can be stacked on top of eachother... so each is full screen all the time, and you choose which one is visible at any given point.
You can also now have "blank" windows with nothing shown... and use "video feeds" to see select portions of the other windows that are behind the current window.
Instant Swap is a major feature that I would be extremely unhappy losing, if I went back to KC.

The power of the mapped keys...
While I didn't switch to IS Boxer for them...
They're the strongest feature, in my opinion.
For example, when I switch from one toon to another it runs a mapped key that does several things.
One is that the current window gets a "High Settings" mapped key run, while the other windows (Target: Windows Other Without Current) run a "Low Settings" mapped key... essentially every active/main window plays with all the eye candy, while the other windows have minimal options for smoother play.

The auto FTL is extremely nice too.
Run a wizard, and instantly have several FTL Keys which can be configured quite easily.
You can adapt this too.
FTL is based off of three FTL keys, which are referenced via a "Do Mapped Key" action.
These are: FTL Target Me, FTL Assist Me, and FTL Follow Me.
The target is usually the Other Windows.
But I've copied the mapped key, and then changed the target to a specific character.
For example, on my mixed team the key is "Priest Target Me", which then allows me to round-robin: Power Word: Shield or Renew via spamming a key a little.
I could accomplish the same, via Clique/Grid and the Repeater Region.

I've not looked at ClickBars all that carefully, since I'm used to what I have and prefer to use the Keyboard as much as possible.
However, you can set a region of the screen to respond to mouse clicks.
Where a click runs a mapped key, rather than a keybind running that mapped key.
And you can choose which graphic to show.
So if you want to have an icon to click, instead of a key to push... that is an option too.

Virtual Files are nice too.
The equivalent of Config.wtf exists for each of your toons.
So you can have whatever sound/video options you want on a per toon basis.
And you can virtualize any file you want, so you could in theory have addons virtualized such that boxing you have one set of unit frames, but when solo and not using IS Boxer and its virtualized files you would then have a totally different unit frame positioning for the same character.