Firstly any form of training is better than nothing.
People train for different reasons, so choose a style that fits with your requirements, i.e. if you want to learn acrobatic kicks and flips then extreme martial arts are for you. If you have limited movement then tai chi is a good choice.
Many classic styles of Kung Fu are based on tournament training which is competitive, fast and furious.
Modern battleground can be described as defending yourself outside the chip shop at midnight where there are no rules no referees and your opponent will not stop until he has caused you great harm.
In many ways modern battleground style of training focusses more on the top end of the violence spectrum, i.e. you are in a life or death situation and no about of verbal dialog will work.
Some people believe that for a martial arts system to work, it must have a lineage that is hundreds of years old. If that is important to then a classic style of Kung Fu does fill that requirement. However certain arts deal with very special high end violence like Defendo which was formulated for SAS soldiers to take out their enemy quickly in wartime. This system could be taught in a matter of weeks, whereas a classical style requires years of training.
Classic Kung Fu has many different stances, low and wide, which outside of classes can be impractical, there are even techniques still taught that have you defending yourself against an attack on horseback. Modern battleground style Kung Fu generally includes medium stances which are more practical in a self-defence situation and it also tends to deal with violence in a much more direct manor with one or two attacks being enough to end a conflict.