Given the lack of experience Sadie Robertson had prior to the competition, the fact that she went to the very end in the competition shows how hard she worked and, for that, I think she's ultimately proven to have performed stronger than Alfonso Ribeiro this season. Alfonso Ribeiro is very talented as well, so he deserves a lot for his part as well, but I think more shows with judges should take into account the person's background and experiences when making a decision instead of solely on the performances.
Sadie Robertson's Mario Brother's dance was creative and fun. It also got rave reviews from the judges. Alfonso Ribiero's routine was more difficult, but it was also more traditional. I thought Sadie's performance was flawless, the idea was really fun, and it made me happy to watch it. It was a break from the more serious side of dancing.
Alfonso Ribiero won the vote and therefore deserves to win. People can always disagree about judging and contest winners, but as long as the winner was chosen in the manner enumerated in the rules, you cannot complain when your chosen candidate loses. Sadie Robertson lost eventhough she obviously has a large following.
I honestly don't think it matters rather one or the other won. I think the point of the show is to entertain people but I don't like reality TV and therefore don't watch shows like this. But to be fair I think one needs to realize that these shows are put together to entertain and elicit conversation. If that was accomplished then the show was a success. It doesn't really matter who wins.