Both can be profitable depending on the movement if the coin and as to how much you would put as capital into the coin. When you are a short-term trader then it may be better for you to choose altcoin because it has a fast movement compared to bitcoin since most of the time, it has a low volume so it has more price volatility than bitcoin bu then be careful with pump and dump because you may end up catching the dump so you would incur much loss and it is riskier to trade an altcoin especially if it has low volume because it may not have any demand in the future.