T5 vs T6

I have ordered a T5 engine in my V90. I grueled over this decision. I found the T6 engine to be noisier and not as smooth as the T5. I also thought I was going to be able to burn regular octane instead of premium fuel like the T6. This was documented in several articles I read. But I have since researched an online owners manual that says both T5 and T6 engines require premium 91 octane fuel. What do you guys think? Is the T5 smoother and quieter? Can I run regular octane in a T5?