Coin flip.
Ballistically - figure 50 fps - 1.5-2gr powder - more w/55.
Long vs. short is the BIG decision, UNLESS you want 156-160s, best in swede, though seafire here throated one or both his SS/MKII Ruger 260s long for them, and it has a tad longer box for a short action.
Lapua - GREAT stuff - in 6.5x55
260 = NOSLER/Norma -Same Same, diff stamp. EQUAL quality at least as far as accuracy IMHO as Lapua 55.
Yep, Swede's are Cool, but NOT usually 'short' though I believe Charlie Sisk did a few short Swedes throated for lighter bullets, BUT it may negate some or all factory Swede ammo from chambering - something to think about - or answer before doing a short 55.
I would ask yourself OP:
Do 'I' like short actions, or no preference?
Do I WANT to shoot the 156-160?
Do I want/need factory ammo? Both made, Lapua via NORMA is loaded to safe max pressures, others not.
Beyond that, if wanting a short action, and bullets 142gr and under, I'd strongly recommend a 260, and if you want better rifle options factory made - w/ammo, then the 6.5 Creedmoor needs included - about equal the 260 in speed - same bbl length.
Lastly, if a short action, and it's a custom build, the 6.5x47 Lapua is a SWEET round, ONLY source of mfg. brass is LAPUA, inc. ammo, across the pond if that does not bother you, gilt edged accuracy, but best w/120/123 - 130s, will run 139-142s but not quite with a 260 or Creedmoor w/o running what some say are very warm/hot loads, and perhaps in longer bbls.
Preference? I like both, AND nothing bad about the Creedmoor or 47, but I like to K.I.S.S.
That said, my newest 6.5mm is a Borden Alpine in 260 no neck turn, NON - ackley, match reamer - has a .100/less leade), custom built, 23" Bartlein, using OUT the Box Rem brass - .5-.6" easy at 100 yds.
When I used Norma mfg. NOSLER brass - I shot my last 4 shots into .196 using a modest 10x scope.
I am happy with it, but ALSO love my 6.5x55 in Ruger #1 K1-A (shot 1/2 MOA at 200 yds) and would never say no to a custom in it, OR a good rifle like a Sako or Blaser though the latter in single shot IS pricey...out of reach for me.
For the dough, you can get a Tikka T3 if found, in 6.5x55 and often get .5 moa or better, using Lapua and quality bullets.
Few 260 factory rifle options, BUT the model 75 I had in a Grey Wolf, shot VERY well.
What RIFLE do you want it in really should determine as they are two close to allow your choice to be made for a mere 50 fps. BOTH are great, but a little different in options.
