Certainly trading with BTC is the safest option. Trading with alts, especially some bump/dump shitcoins, very easily fills the bag with worthless numbers of some promising projects.
Trading with extremely volatile altcoins can be very risky. You are going to have to execute your trades well and timing is very crucial in here. Not everyone can trade these very volatile altcoins regardless of how profitable they can be. Altcoins that are less volatile can be traded easier like ethereum for example.