Are there any advantages to having a 'long' name but going by a nn?

[Sannebanana]

I'm trying to decide between Anouk and Anouska at the moment. TBH if I go for Anouska she will probably still be called Anouk as a nn, so am I overcomplicating things putting a longer version on the birth certificate? I think Anouska might be easier to find a middle name that works with it, but if DD is never going to be known as that then is there any point?
Thanks

DD has a 'toddler name' but a proper one on her birth cert.

I've got a long name but usually use a diminutive; it's especially useful on the phone, because the one-syllable short version is easily confused with other names (e.g. if I was Katherine nn Kay it could easily be misheard as Kate so I'd use the full version).

I tend to use the full version for work, but that's not hard-and-fast - the shortening's not fluffy, (equivalent to Kate rather than Kitty) so I don't mind clients calling me by it. Also I still feel as if I'm being told off when I'm called the full version, which is silly because I used the full version until I was a teenager, then experimented with different shortenings until one stuck.