The Harley-Davidson X440 will be a good starting point for a novice rider, although you will take some time to get used to its weight. Since you are shopping in this class of bike, other options to consider are Royal Enfield Hunter 350, Honda CB350 trio and the TVS Ronin. Of these, the Ronin will be the lightest and one of the most affordable options while still delivering comparable performance to the 350s. 

The Yamaha Aerox 155 is a good scooter in many ways, but its stiff rear suspension and cramped ergonomics for taller riders are two big reasons we would steer you away from it. If you do want a large-capacity scooter, then the TVS Ntorq 150 is our current pick because it has engaging performance but doesn't sacrifice comfort or practicality. 

Take a test ride of everything you consider, which will help you decide if you're ready to get into bikes or should stick with a scooter. 

Since you have had such a lovely experience with your Dazzler, you could play it safe and replace it with the Honda Unicorn / SP160 - both of which can trace their roots back to your machine. Other options for you in a similar displacement bracket are the TVS Apache RTR 160 4V and Bajaj Pulsar N160. 

Coming to scooters, we would recommend the TVS Ntorq 125 or Ntorq150 - depending on your budget - both of which are sporty, capable and comfortable scooters that will stand out from the crowd. The only reason we would steer you away from the Yamaha Aerox is its stiff rear suspension, which will get tiring and downright intolerable if you stay in an area with less-than-perfect roads.