The standard jp necks are typically unfinished maple while the BFR are typically mahogany with matching finish. Some prefer the unfinished neck because its smoother, but I feel the finished neck on my BFR is very easy to navigate as long as i keep it polished/buffed. If i let it get too oily then it can be "sticky". Some BFRs do come with the roasted maple neck also which is supposed to be really stable in variable weather.
i recently played the JP13 and I thought the neck feels very different from both of my jp6s. It feels more "refined" with the polished edges. Maybe it's perception but it also feels a little chunkier than my jp6s.