When the folks at White's engineered the new version using the excellent analog display, their goal was to make a detector that would match or better the performance of the former 6000 Di Pro SL, and have it 'fit' in the smaller housing used by the XLT, Quantums and Classic SL series.
The result was the 6000 Pro XL.
About a half-dozen years ago, they revamped the names of some of their models, incorporating the E-Series and a Pro series. To achieve this, they renamed the Classic IDX the IDX Pro, and they dropped the '6000' from the outer appearance of the 6000 Pro XL, then reversed the name to have the XL Pro.
So, all they did was change the 6000 Pro XL to simply the XL Pro.
However, the Operator's manuals and the sticker inside the battery access door still had the '6000' included, and that added to the confusion.
In the end, however, other than naming confusion, there is NO DIFFERENCE in electronics or performance between the 6000 Pro XL and the renamed XL pro.
Monte