Actually, I would like to know what kind of trader he is before suggesting here. If he is a day trader, then I will suggest him to use centralized exchange because in this case the amount of trade is high and in this case it can be seen that centralized is one whose trading fee is very low.
This is why it is more profitable for day traders to use a centralized exchange. On the other hand, if you have to use a decentralized exchange, in this case, if you pay the fee repeatedly, it can be seen that a huge amount is going into this exchange fee, which is actually not beneficial for trading. But if long term holder then it will be best for him to use decentralize exchanger.