A majority of fics don't even happen in the same universe as the actual show anymore. I think when fanfiction first started, the writers kept their pairing in the same universe as a sort of wish fulfilment on the shipper's part and for several reasons that range from their pairing not getting a fair shot (crack ships) on the show to just having continuing/building on the show during and after the show ends. The more people wrote, many started writing about characters that barely resembled those on the show except in name only.
When it comes to Nick/Adalind vs Nick/Juliette, I don't think one pairing outmatches the other, it's likely that Nick and Adalind now has a lot more recent fics because the show finally went in that direction. Before S5, they were a "crack" ship and their fans didn't have much to go on other than to write their own stories. Nick/Juliette may not be seeing an influx of new fics or new fic writers because S4 left such a sour taste in viewers' mouths. This could be because those who supported them gave up on the show and weren't interested anymore or the demand for new stories was low in light of the show's developments against Nick/Adalind.
Fanfiction isn't an exact science, people write for any number of reasons and that may relate to more fics for a certain pairing compared to another but without finite data, it's generalised area. SN and TVD have some of the largest fic numbers for Destiel and Delena but one is a "crack" ship while the other is "canon" to show you just how inconclusive fanfiction is.
When it comes to Nick/Adalind vs Nick/Juliette, I don't think one pairing outmatches the other, it's likely that Nick and Adalind now has a lot more recent fics because the show finally went in that direction. Before S5, they were a "crack" ship and their fans didn't have much to go on other than to write their own stories. Nick/Juliette may not be seeing an influx of new fics or new fic writers because S4 left such a sour taste in viewers' mouths. This could be because those who supported them gave up on the show and weren't interested anymore or the demand for new stories was low in light of the show's developments against Nick/Adalind.
Fanfiction isn't an exact science, people write for any number of reasons and that may relate to more fics for a certain pairing compared to another but without finite data, it's generalised area. SN and TVD have some of the largest fic numbers for Destiel and Delena but one is a "crack" ship while the other is "canon" to show you just how inconclusive fanfiction is.