Too close to call, in my opinion. The MON has a significant speed advantage, which is offset by the WLF's longer reaching LL and thicker armor. Terrain will likely play a part, but I suspect it would mainly come down to player skill and playing style.
Note that any time the MON wins Initiative, it can dictate the range, and either close to 1-3 range, or at 6 where the LL gets the same range penalty as a ML, and the WLF can't fire the LL and even 2 MLs on consecutive turns without heat issues. That puts them at pretty much equal firepower on average, with 1 point better to-hit odds for the MON versus better ability to soak a few hits by the WLF. Ultimately, it will likely come down to WHERE the occasional hits land, and how well or poorly they're grouped or spread.
That said, while the WLF is a great design, I'd slightly prefer running the MON, purely as a matter of playing style. In essence, the WLF is a lighter version of a PXH-1K, while the MON is a heavier and much harder-hitting LCT, which are also favorites of mine.