I have never lived in Dhaka, I have visited Sylhet a number of times. I liked it their I thought it was very comfortable. They have their own aiport from which you can travel to differnt parts of the world, now they even have their own plane Air Sylhet. They have a local train station, bus station, lots of travel agents doing cheaper flights to differnt destinations.
Lots of tourist attractions like, Dreamland, Tea Plantations, waterfall, Projoton and many other theme parks, lots of shopping centers and the most pious and religious places Shajalal.
I enjoyed the 4 weeks that i spent there, i thought it was a lovely places.