Considering you have some back pain, we would recommend you stick with a motorcycle as the big wheels, longer-travel suspension and neutral riding ergonomics will keep you shielded from road imperfections. Inside your budget, we would recommend 125cc bikes like the Honda Shine 125, Hero Super Splendor / Glamour models, TVS Raider 125 and Hero Xtreme 125R. Depending on the sort of style you are after, you can choose between any of these. 

Since you have asked us about a scooter, our current top picks are the TVS Jupiter 110, Suzuki Access and Honda Activa 125. While the scooters will be more practical, they will not be as ultra comfortable as a motorcycle over bigger bumps. 

Take an exhaustive test ride before you decide. 

Since you are learning to ride and haven't specified your budget, we will stick to recommending 125-150cc machines as they are affordable, fuel-efficient and beginner-friendly. Since you want a bike that stands out from the crowd, we would recommend considering the TVS Raider, Hero Xtreme 125R and Honda CB125 Hornet in the 125cc class. All are peppy, frugal and have catchy styling while being very easy to ride. All three come with single-channel ABS on at least one variant, and we'd recommend going for one of the ABS variants, considering you are a newer rider.  

In the 150/160cc class, bikes like the Bajaj Pulsar N160, TVS Apache RTR 160 4V, Suzuki Gixxer and Honda SP160 would be a good bet.