Since you haven't mentioned whether or not you want a bike in the same category or want to move up, we'll give you a broad spread of options to choose from. 

In the 100cc commuter category, bikes like the Hero Splendor, HF Deluxe and Passion, Honda Shine 100 models and the Bajaj Platina 100 remain compelling propositions for their blend of frugality, comfort, dependability and low ownership costs. 

If you want to move up to a 125cc bike, then the TVS Raider, Hero Xtreme 125R and Honda CB125 Hornet would be our recommendations. Since you've said you want a sporty look. 

Take a test ride of these bikes before making a decision. 

Both the bikes you are considering are some of the best machines in their class. So you're already starting from a very good point; therefore, here on out, it will depend on which bike fits you better as per your physique and has the features and look you prefer more.

The Honda CB125 Hornet has some unique features like the golden USD fork, a crisp TFT display and excellent fuel economy. However, it can feel a little tight for larger riders, so depending on your height, it may not be the best option for you. 

The Hero Xtreme 125R is the only bike in the class to offer you dual-channel ABS on select variants. Also, it is a little more affordable than the Honda bike, so if those things matter to you, then this makes for a better purchase. 

A test ride of both will help you decide which is better for you. 

The Honda CB125 Hornet makes a good case for itself as your first bike with its lightweight, frugal engine and flashy style. You should also take a look at the Hero Xtreme 125R and TVS Raider because there are some areas where these bikes have an upper hand on the Honda. 

Bigger bikes like the Bajaj Pulsar NS160 and Yamaha MT-15 will offer you more performance, albeit at the cost of fuel efficiency. They will also be a little heavier, but it won't be a big difference. 

A test ride and a clear expectation of what you want from the bike will help you decide which bike is best for you. 

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.