Ah, "Sweet and Elite". If "May the Best Pet Win!" is Rainbow Dash at her best, this is Rarity at hers. There's substantial character development, as well as an excellent conflict, a great song, humour, and some very nice animation. It comes pretty close to being a perfect episode.
As usual, first let's talk about the lead character. Rarity is wonderful here. She faces understandable dilemmas, and while they may not be relateable in their literal form, there's probably some element to choosing between friends and something else important that most people can relate to. Meanwhile, her ultimate decision shows the character development she faced in her experiences with the Canterlot elite. She's characterized very strongly in this episode, and it serves as a precedent for how the character should be written.
The episode also boasts great humour. Moments like the Canterlot elite's curious laugh and Twilight's awkward dancing are memorable and highly amusing, and they litter the episode. As such. "Sweet and Elite" is a very fun episode, and highly enjoyable on top of its strong characterization-"Sisterhooves Social" could have served to learn from it.
Then, of course, there's the song. It's catchy, it does a good job of representing Rarity's character, and it's altogether an enjoyable listen. Of particular notes are the harmonies of the chorus, which work wonders with Rarity's singing voice.
There's very nice animation here as well, with a few great subtleties about. One that caught my eye was a small moment where Rarity scowled for just a few seconds as Hayseed turned away before ceasing to scowl that I found particularly amusing. Subtle touches like that may go unnoticed by the average viewer, but they add a nice little touch to the show's visuals that just makes them that much better.
"Sweet and Elite" is an example of the best MLP has to offer. It's superb in just about every aspect. After the previous episode, this is a particularly nice treat. It's got a fun song, a great story, and a great song on top of that, and all around it's an excellent package.