Bitcoin is the strongest cryptocurrency, so it is obvious that bitcoin is more safer and more profitable. Bitcoin is also the most popular cryptocurrency in the world. I prefer to you to buy bitcoin than altcoins.
There is no such difference in between bitcoin and altcoin. Both are equally profitable and can help you earn some handsome amount of money too. The thing is it is you who has to decide this thing that whether you are in a mood of doing long term investment of money or you are interested in day trading. For holding, bitcoin is more suitable option while for day trading, altcoin is more suitable option.