After thinking about this for a few mins I can't even remember which one I think is more normal, however, for me "snuck" is certainly not jocular or a non-standard form.sneak (verb)
Its origins are shrouded in mystery ... From the beginning, and still in standard British English, the past tense and past participle forms are sneaked. Just as mysteriously, in a little more than a century, a new past tense form, snuck, has crept and then rushed out of dialectal use in America, first into the areas of use that lexicographers label jocular or uneducated, and more recently, has reached the point where it is a virtual rival of sneaked in many parts of the English-speaking world. But not in Britain, where it is unmistakably taken to be a jocular or non-standard form.
I'm curious as to what other BE speakers make of this quote and if they agree with it or not.