The question is asking if
Nargothrond or
Gondolin played a greater part in the
Nirnaeth Arnodiad but in the war against
Morgoth as a whole.
'
Finrod' and Nargothrond are the instigators, naturally, the instigators play the more important part because if it wasn't for the 'instigation' then the
events that took place would not take place at all.
I will deal with the Silmaril first, though there are other occasions in which Nargothrond plays the more important part in the fight against Morgoth. The 'Quest of the Silmaril' hinged upon Nargothrond-no Nargothrond=no successful capture of the Silmaril. Why? Well, Nargothrond first of all, acted as a impetus for
Beren to at least attempt to achieve his quest, rather then wandering around aimlessly. His visit to Nargothrond eventually lead to the capture and imprisonment of him and his companions by
Sauron.
'Nargothrond' was also the place where
Curufin and
Celegorm fled to after being over-whelmed in the Daggor Bragollach. Celegorm brought with him Huan-without
Huan the Quest of the Silmaril would have failed. They also played there part in the Quest, setting up the events so they transpired as they did. Without their interaction the quest would have failed. It also woke up the Silmaril lust in the Fëanorians, which led to the Second and Third Kinslayings, which lead to Elwing meeting
Eärendil at the Havens on Sirion, but more importantly it led to the gain of the Silmaril. It also led to the eradication of Sauron from Tol Sirion and the freeing up of that area from
evil, for a while.
Simply, if it wasn't for Nargothrond the Quest of Silmaril would not have succeeded. No Silmaril=no purpose for
Turgon. Sure he could live secure in his
realm for a while, but ultimately they lost their purpose with the Silmaril.
Finrod is
the one who greets
Men to
Beleriand. Finrod is the one who gains access for the Haladin to live in Brethil. If the Haladin didn't live in Brethil then
Húrin and Huor never would have went to Gondolin or existed, maybe, since their mother, Hareth was a Haladin, but also the reason they went to Gondolin was because they were in Brethil and they were separated from their companions in the
Dagor Bragollach. No sojourn in Gondolin by Húrin and Huor has several consequences. Maybe they wouldn't have held the Fen of Serech for Turgon to pass, since they would not have any prior knowledge of the importance of Gondolin and Morgoth would have no real reason to capture Húrin, so he wouldn't have found out where Gondolin was like he did and mayhap Maeglin wouldn't have been captured and thus the
Fall of Gondolin may have been delayed, since Morgoth increased his spies there after Húrin’s cries showed him the vicinity whereby Gondolin was located. That 'Tale of Turumbar' would also be non-existent, so there goes one of the most important stories in the
History of Arda.