You'll read the phrase "Dial it in" alot on this forum. Many times a small adjustment will dramatically affect your comfort (structural ridgeline length, underquilt taughtness ect). I think you'd find that you could get comfortable in a SN but, the DN will have a larger margin for error or "sweet spot". It will be easier/faster to "Dial it in" with a DN.
Either way you'll learn alot.