XP is King Kutters line of equipment designed for limited Cat 1 three point hitches. Nothing to do with gear drive or extra beefy. Notice the "sub compact" sticker on the back of the tiller.
The lower lift arm aka lower link pins have a slightly less wide spacing. There maybe other dimensional differences also. I had a phone conversation years ago with a King Kutter customer service person which was helpful.
Here is a video , important part showing the spacing of the lower lift arms pins is within the first minute to minute and half. He measures the width at about 20 inches versus a standard Cat one spacing of 26 inches.
watch
I purchased a King Kutter XP box blade and XP landscape rake for my B7100 and they fit better than my standard Cat 1 back blade. I have also used my XP King Kutter implements on my L2501 and the lower lift arms angle in a bit in comparison to standard Cat 1 implements.
There is also a difference at least in the box blade and rotary cutter for the XP as far as weight and the heavy duty build aspect.