Yet that i5 will be way faster than whatever ARM is in Galaxy. It will also have much faster SSD than the eMMC in phones, and will be paired with faster RAM to boot.
All these things take way more energy, so your laptop will also have much bigger battery.
Some exception cases: the phone needs to run a Mobile device management agent that installs and launches an antivirus, or the mobile happens to connect to a corporate VPN that routes all traffic and then inspects it via some appliance.
So Ghz is Ghz regardless of x86 or ARM as thisvis just the clock speed.
Another discussion is how much work is done each cycle. For that you might use GigaFLOPS or TeraFLOPS (10^9 or 10^12 dloating operations per second) or another absolute measure of performance.
All these things take way more energy, so your laptop will also have much bigger battery.