That's true the purpose will decide the bike to be chosen.
Both bike has different styling and meant for different purpose. Well if you look at the technical data both has little difference; GT is little more powerful than CLASSIC. Well that is reflected while driving. GT is more over a city ride bike and has sporty stance, whereas CLASSIC is built for some adventurous ride.
Both bikes can be used for pillion riding. The rear seats is available in showroom as an accessories.
If you are not a heavy built person with strong arms than at higher speed you may loose confidence in case of CLASSIC; although CLASSIC is meant to built for so called "ROYAL" riding, so for normal speeds this bike is best.
In case of GT the seating position is moreover like a sports bike, so at high speed you are lean to the aerodynamics of the bike.