The Ultra XL and Ultra Lead are very different modules, and not really intended to be grouped together.
The Ultra XL -- along with the original Ultra -- is an attemp by Randall to produce an over the top, hi gain tone. Think detuned, nu-metal, chugga chugga stuff. The main difference between these two is that the Ultra has a scooped midrange and the XL does not.
The Ultra Lead, on the other hand, is not a modern hi gain tone. It is a very smooth, midrange dominant module that was intended to be used for solo work. To me, it sounds like Carlos Santana playing lead through his Mesa Boogie Mark series amps.
