It is advisable to use a bigger screen when trading. It will help you read the charts better and it's more convenient to use than a cellphone. I'm guessing you're asking this question because you're planning to start trading and you only have a phone for now? Just a piece of advice before you start to trade, do a lot of research. Practice with dummy trading accounts first and have a mentor. These will help you succeed in trading and be profitable.
In my opinion, both have different advantages, when we start trading via a laptop our level of focus is better protected from the distraction of any notifications that come out of the monitor screen, so we can easily and focus on trading, but when we trade via our cellphone it can be easier to access wherever and whenever we need, because on our cellphone it is faster for us to monitor the movement of the graph itself, when we have free time we can directly access our trading via cellphone, if we don't have a laptop we can take it wherever we go If the cellphone is of course with us for almost 24 hours, that way both have their respective advantages and can be used with both.