let me lay some jeep lingos on ya...
long drive comfort
i had a tj wrangler before (older model) and i have a wj grand cherokee now... i only test drove the SWB jk so im basing my assessment on these...
the swb jk drives alot better then the tj did... so i can only assume that the lwb jk could be quite good... definitely better a hilux (older model).... but not as comfy as merc E320... never been on a sierra on long trip before so i cant compare to that...
end of day, comfort factor is very subjective... at times i thought the tj drove a lot better then wj, but thats a different story... so best to test it out yourself...
noise factor
NFI, the dealer wasnt too keen on let me drive too far, they knew i wasnt going to buy one

someone might answer you on that...
with soft top... its basically a small tent on wheels, you do the maths...
boot size...
how much tools do you bring... its a decent size, but never big enough... i guess, really pends on what you bring... they are quite sufficient for weekly shopping...
roller drawer? there maybe some, but i havent seen any, for the first time ARb and other local manufacturers actually started making accessories for them on release rather then 10 years later like the TJ's... so my bet is not too long now...
wheels (stud pattern)
i would sell the sierra tyres and rims...
they JK stud pattern is 5x5.0 (5x127)... size im pretty sure its 16x7 bs is approx ~5.75" or there about... (stock rims on WJ is 5x5.0, 16x7 bs 6", and i fitted a set of jk rims on there and the bs is almost the same, and my mate measured it to be about 5.75 or something like that) some jk spec comes with in 17x7? rims
some might argue that you can fit 15's on them... i never tried so i don't know...
you know what... best to go to the dealers, bring a measuring tape and poke you head in one of them and see what you think...