The VK SDK is a iOSlibrary for working with VK API, authorization through VK app, using VK functions. To authorize via VK App you need to setup a url-schema for your application, which looks like vk+APP_ID (e.g. vk1234567).
Twitter Kit is designed to make interacting with Twitter seamless and efficient. Displaying Tweets, logging someone in, or Tweeting from your app is all made easy with Twitter Kit's components. Twitter Kit provides views for Tweets and live timelines, and a composer that makes sharing from your app simple with a few lines of code.