I'll vote for Sherry. As a huge Beach Boys fan, I should vote for Surfin' Safari for its historical significance, but I look at their first two albums and singles as "amateur record" . It's Surfer Girl (both the single and the album) that established professionality of Brian as producer.
On the other hand, Sherry, which sounds somewhat old and childish today, is a 'professional record'. That rough drumming catches your ears at first. Then, THAT falsetto by Frankie Valli - they shows their professionalism they've gained for some ten years of unpopular singles and daily tours. Great stuff.
If "Sherry" ran against "Surfin' USA", which is twice as catchy, it'd be the choice. Trouble to like "Surfin' Safari". "Sherry" liked instantly. I discovered it via Stars on 45's "Golden Years of Rock & Roll" medley, starts at 1:06:
https://www.youtube.com/watch?v=a1elCkkPv-AI say "Hey I like it!", read the info which songs sung in the medley, find it & listen. It led to me being Four Seasons fan. Banal maybe, I do think "Sherry" is their Top 10 song, if not Top 5. It doesn't sound "old and childish". If it does, "Surfin' Safari" too. Many 60s songs bound to get such perception today. If smb. told some song is too ancient, it will not stop to be liked.