Still, using a dedicated smartphone as a Bitcoin wallet does not make it as secure as a hardware wallet (which is designed to be entirely offline and immune to online threats).
Using a smartphone but never connected to the internet is 100x times better than a hardware wallet cause that is what cold storage once its connected to the internet then whatever data is in the device become vulnerable to attacks so if possible have one specific device which you should never connect to internet can be considered as 100% immune to any vulnerabilities like malicious links, clipboard hijacker and anything else.