Actually the difference is in the size I found most recently. First, I received 2017/18 FT Descendent 4, 27.5 size. I picked online the size based on my conventional boots size true to my 270+ mm feet. What I found is that FT 27.5 mondo size is not the 27.5 size conventional ski boots. Later are about 4 mm larger (longer) than FT. Then went to the local store and confirmed my suspicious that FT are running shorter comparing back to back with conventional ski boots. Somewhat surprisingly the narrower with wrap liner lower volume shell of 2019 FT DropKick 6, 28.5 size fit my feet better than 27.5 higher volume and 102 mm last. Not only because I tested one size larger DropKick, but the ankle cup inside the liner formed by J-bar was fitting without pressure point my ankles compared to the ankle pressure point I felt with Descendent 4.
With other words the claim in this forum that all FT models are practically the same is an overstatement softly put. The claim that the only difference between FT models is the shell volume (i.e., Evolution series vs. older Classic narrower built FR models) is true to some extend only. Sure, make sure you test FT first before going online and buy for much less. For example, I got the most popular DropKick 6 online for $200 less than offered in the store, while the cheapest model, Descendent 4, was on sale after the season for the same price as online practically. Buying in the store with boot fitter never worked for me, the most problematic ski boots I used was exactly among the conventional boots picked and customized (shims, etc) by so called mass boot fitters in ski stores around the CA Bay area. While testing by yourself first knowing the details in choosing ski boots, then going and buying online was the most successful procedure for me. Assuming also, I do not have any special needs feet, so after purchasing online the only thing needed was replacing the manufacturer’s insole with green sure-feet, that’s all.
While picking FT model ski boot requires knowledge of few things more since this is the only truly customizable ski boot brand excluding the fully moldable shells. First, one should know that FT boots are marketed primary to park and freeride younger ski crowd, which discouraged many of the other skiers of looking at FT brand. I was one of the mislead skier to believe that FT is not a ski boot for all-mountain skiers other than park & freeride fans. After a detail research online I realized that FT are for everybody else who is looking for comfort, performance and customization, and for that one does not need bootfitters. The bootfitters are helpful for the conventional ski boots that are only partially and difficult to customize without true shell & liner molding. With FT once you find the right mondo size, and whether you fit narrower classic FT model (99 mm packable to 100-101 mm last after a few days skiing), or the newest higher shell volume and wider last Evolution models (102 mm last) addressing wider public. Other detail with FT is that narrower Classic, DropKick and other narrower models (99 mm last) with wrap liner has performance insole also, so do not hurry to replace it with Surefeet anatomical insole before packing the liner first. While Descendent men’s models and women’s models among the Evolution series have flat, not supportive insole and more conventional type of liner with tongue like the conventional ski boots.