This may be a biased opinion, but here goes....
Plushest? Probably the Salty or Flux (I haven't ridden the Flux, but am very familiar with the 5-spot). Salty is the most versatile (can be a 5" burly trailbike or 4" singletrack screamer if desired). RacerX is probably the "fastest". My 4" Salty weighed 26lbs with tubeless wheels and TALAS fork, Maguras, and XT drivetrain. I now have it in 5" mode-the new RP3 rear shock and new TALAS makes it ride almost as well as the 4" bike, but it can go through the roughest trail at any speed with minimal input-the bike can do no wrong. It still retains XC crispness with the long travel and stability at speed that I have never encountered on any other 4/5" bike. A true "hero" bike. I still have the 4" rockers-combined with the TALAS, I can dial the bike down for superfast XC riding, but for general all-around trail riding, the 5" Salty can't be beat. I almost purchased the RacerX, but I gave up a smidge of efficiency for more trailbike performance (this was before the Motolite was available). I almost went with the 5-spot, but I wanted a 4" or 5" option, and could get a better price on the Ventana. Plus, Sherwood is great to work with, and they are probably the best built bikes on the market, bar none.
Still, for fire road riding, you don't need 5" of travel-the Racer X would be the better choice here. If you are vacationing in Moab or Tahoe, the extra travel is very handy. I really don't think you can go wrong with any of these-they are all superb choices.