Replying to Help!! Faction 3.Zero Length?

So I've found a sweet deal on last season's 3.Zeros which I've had my eye on for a long time, particularly as Faction are not making them for the 15/16 season.

The only issue is that I'm torn between the 175 and the 183. Normally I'd try to test both but I'm UK based and the deal expires at the end of August so not really an option!

I'm 5'8'' (173cm) and approx. 160lb. I don't have dedicated pow boards at the moment so these would be my go to skis for deeper days. I'm planning on putting Guardians/Trackers or Adrenalines on them to use these as my touring set-up. Most backcountry I've done up till now has been lift accessed / hiked in the Alps (mostly Verbier and Cham) but planning on doing more touring and will hopefully be living in BC from next year so should have more opportunities to get out into the backcountry.

My current day to day ski is the Faction Heroine 09/10 model (which is pre rocker being added to the ski) in 169cm, which I love but do find a bit short. I'm leaning towards the 183 as the whole point of getting the 3.Zero over the Candide 3.0 is that I want a hard charging ski and I'm worried that the 175 won't be long enough with tip and tail rocker in the mix as well. BUT is 183 going to be less versatile? Also, as a touring newb, do I need to think about sizing for length differently at all? (I'm not too worried about a few grams of weight either way given that I'll have frame bindings on them anyway)

What do you reckon Newschoolers?