UX or UI? Which one is better?

UX or UI? It's like asking "cake or pie, which one is better?" 
Often times I get asked, how would you define UX and UI? Are they the same? Which one is more important? 

My answer... 
Ever owned a horse? Ever held the reigns? What would you do with them if you do not know how to ride a horse? Trust me I've tried being on both ends - starting afresh and taking lessons. It makes a huge difference when you know the A-Z of something. Knowing how to hold the reigns, how to ride the horse, reign your cattle is what matters! User Experience entails all of that. Although good UI is your reigns, but your riding lessons are your true UX skills.
Still puzzled? Don't be! It is really simple. Read on...

Good user experience is learning all the ropes of great end-to-end product design and applying your knowledge of functionality, scalability; ultimately leading to success. How a button looks establishes visual interface, but how it functions and where it leads a user, establishes it's very own purpose and several different action items. I believe user experience and UI are important in their own stride. 

Functional products with great scalability features enable longer product lifecycle, retention of users, and company success. Visually appealing interfaces add that much value. Always remember, that which is beautiful but not usable, will not impress the user. Your customers/users are your true patrons. Designing UX and UIs with the "U" in mind will always ensure success. 

User experience is this whole big puzzle. UI is just a piece of this puzzle. Try solving it without all the accurate pieces and you end up with a mess. Add interaction, visual design, product design, good content and functional engineering. Voila! Your puzzle is now complete.