Uber Premiere Car. Which is better?

We need a new car and considering getting one that will get me into Premiere. Looks like the cheapest is a Cadillac XTS. Even if you qualify w this does that effect the rides Uber sends you? I’d imagine a newer GLS would get more Premier rides offered than a 2016 XTS. What am I missing? Also do tips increase w Premier based on how nice your car is?