Don't know anything about the F&P. Never seen one. Don't recall any posrings on them. Might help garner comments if you can post a model number.

Comparing Bertas and NXRs is a bit like comparing high-style Italian-made sedans (Bertas) to basic, manual-everything, industrial styled imported high-lift 4wd pick-ups for ranch work and off-roading capabilities (NXRs).

Bertas are sleek, counterdepth, euro-ranges. Used
to be that you could get them in colors. I suppose you've already tried searching for threads? (Sometimes helps if you go out to google and use a search string like "gardenweb + berta"). Have you seen this current thread?

http://ths.gardenweb.com/discussions/2981897/any-users-reviews-of-bertazonni-36-gas-cooktop-or-rangetop?n=9

They have narrower cooktops (that's the
counter-depth part) with some peculiarities in operation of the cooktop
and oven. Don't know anything about LP conversions of Bertas. If you
like the Euro-style appliances (narrow cooktops, small ovens, etc.), you
might look into the Ancona ranges at Costco. More Italian euro-style
equipment but about half the cost of the Bertas.

Most of the NXR postings here have been about the 30" models. Friends of mine on the coast have had a 36" NXR since 2009 and are still pleased. I've had my 30" model for going on three years now. Don't know much about the LP conversion kits except that Costco.com carries them as extras for (I think) around $50. We've had some postings here from folks who had the LP conversions done for them by their vendors and a couple of those folks weren't happy with the quality of the conversion work. Otherwise, the NXR seems to be favored more by the DIY crowd. Great for those who like those capabilities and have the ability and interest in doing their own maintenance and repairs and/or fiddling when and if needed.