In the price range you're looking at, there are a variety of options in different body styles, so we'll list them out for you. If you want a sporty road bike, then options like the KTM 390 Duke, Royal Enfield Guerrilla 450 and Triumph Speed 400 are the way to go. Do bear in mind that the KTM can feel quite cramped for taller riders and, over longer stints in the saddle, this will become even more pronounced. 

If you are leaning toward an adventure bike, you should be looking at the TVS Apache RTX 300, Royal Enfield Himalayan 450 and KTM 390 Adventure models. The RTX will feel the slowest because of its smaller displacement, and it also weighs 180kg. 

Since you have a long commute from time to time and are a taller person, we would recommend you steer clear of sportbikes and cruisers. Also, stick to roadsters or adventure bikes, as they will be more comfortable. 

A test ride of the above mentioned options - and anything else you may shortlist - will help you decide which bike is right for you. 

If you want an adventure bike that is E20 compliant, you will need to either purchase a new bike or search the pre-owned market for a lightly used model manufactured within the last 1 or 2 years. 

If you are looking for a new bike, we would recommend paying the high initial purchase price of the twin-cylinder Honda NX500. It is a rather sorted machine in almost every regard and will feel like a nice step up from your single-cylinder KTM. And since you're familiar with the trouble-free Honda big bike ownership experience, the NX500 makes for a logical step up. 

If you decide to go for something a little less pricey, then bikes like the latest KTM 390 Adventure models and the Royal Enfield Himalayan 450 are also options worth looking at. 

You also have the option of waiting for the new BMW F 450 GS, although its pricing will be similar to the Honda bike rather than the single-cylinder models mentioned above.

A test ride of everything you shortlist should help you make a decision. 

There's no way to accurately portray how much the maintainance cost of the BMW F 450 GS will be, as it is yet to be launched. However, BMW bikes have a reputation for being a little pricey to live with, even the smaller 310s. You shouldn't expect the F 450 GS to be as easy on the wallet as its peers, like the Royal Enfield Himalayan 450, KTM 390 Adventure models or even the Honda NX500. 

We recommend you wait a while before you buy the F 450 GS so that you can see thorough reviews of the bike. Also, you can speak to actual owners of the machine, and then make an informed decision. 

Since you mentioned you have long commutes, and you want something fairly engaging to ride, we'll recommend a mix of ADVs and comfortable roadsters. The new TVS Apache RTX 300 makes a strong case for itself as a single bike to do everything. It is definitely something that should be near or at the top of your list. 

You can even take a look at the KTM 390 Adventure models and Royal Enfield Himalayan 450 - both are quick, comfortable and have great long-distance capability. 

If you want a more road-biased bike, then options you can look at are the Triumph Speed 400, Royal Enfield Guerrilla 450, TVS Apache RTR 310 and KTM 390 Duke. Depending on the balance between performance and looks you want to strike, they all have something unique to offer. 

Take a proper test ride of all bikes you shortlist before making a decision. 

Let's dissect each bikes strenghts and weaknesses so you know what you're in for. The TVS Ronin is a relaxed, comfortable, peppy and relatively fuel-efficient machine. If you don't mind how it looks, the Ronin is a machine that will keep you satisfied for a long time.

The Yamaha XSR155 is essentially a handsome MT-15 with some small ergonomic changes. It is the sportiest machine of all the bikes you're considering and that reflects in its canted forward riding position and stiff suspension setup. If you have good roads around your residence, then the XSR makes for a compelling purchase.

The Royal Enfield Hunter 350 and the Honda CB350 H'ness are similar machines with somewhat familiar riding experiences. Both are comfortable, look good and have big, torquey air-cooled engines. The difference is that the Honda feels like a more substantial bike that needs a little more effort when riding, owing to its super tall gearing - not necessarily a bad thing, if you're into this sort of thing. 

The Hunter will feel smaller, lighter and more flickable inside the city. Additionally, its well-judged gearing will ensure you don't have to make many gear changes. 

Take a comprehensive test ride of all 4 before you decide.