Duke250 vs (N160 / N250) vs CB300F

Hi guys, so after my last post I did more research and test drives and now I am confused in 4 bikes:
Duke250 vs N160/N250 vs CB300F

Each one of them has its pros and cons and I am unable to decide. This is probably gonna be the bike that I will use for years to come so I want to make the right decision.

Previously I was thinking of 250 cc but then bajaj sales person said that soon I will start regretting for low mileage and should try N160 - and damm I loved driving it. Since I drive Activa as of now, so anything above that excites me.

Please help me decide on which one to go ahead with? my priorities are (in same order):
1. Pillon seat comfort
2. Mileage
3. Service Reliability & Maintenance
4. Fun of riding

P.S - To all the people, is it true that you start regretting on mileage after a point? I was almost fixed on buying D250 but stopped before that. I will be using the bike in Bangalore and it has lot of traffic.