I've spent a lot of time with 28mm tires, but I'm absolutely in love with my 38mm GravelKing slicks. I don't really notice much speed difference (if any), and t

I've spent a lot of time with 28mm tires, but I'm absolutely in love with my 38mm GravelKing slicks. I don't really notice much speed difference (if any), and the comfort level makes up for it if there is. I ride for fitness, so I'm happy. More details in my other comment (I actually ride a gravel bike so I have the extra clearance for big fat tires if I need).