I've not used either Samsung or iPhone due to personal reasons, but when it comes to trading seriously, you would want to go for a laptop instead.
The main reason is that charts are way more easier to read on the larger screen compared to phones. Also, you can trade without doing your own analysis, that's a recipe for failure in the long run, but you can't develop your own strategy or verify calls if you don't know what to look out for.
On a laptop, you can go to sites such as Tradingview, use the tools available to draw support and resistances, trend lines, use indicators of your choice to confirm whatever signal or bias you have before taking a trade. This is very hard to do on a phone as some of these features are not available on the mobile version.