For me, the common difference of bitcoin and altcoin is a bitcoin has higher value but hard to earn while an altcoin has a lower value but easy to earn. If you want to earn bitcoin you should work hard. Also, if you want to invest, bitcoin is harder to invest than altcoin. Even altcoin has lower values than bitcoin you can have more altcoin faster. But on choosing which cryptocurrency you're going to use, it is your choice.