I believe the single pole switch could be dangerous if for some reason the neutral becomes live, and the user is poking inside the unit with the power cable still connected.
On paper it is more dangerous but truth is, if one doesn't know electrical safety then they shouldn't be opening things up.
In my opinion a more important safety aspect that sometimes is not addressed properly on diy builds is to make sure there is a good connection to safety earth throughout the entire chassis. On many off the shelf enclosures the grounding is often undetermined so one needs to remove paint work / anodisation or add wiring. I wish some manufacturers charged a little extra and provided parts that have been masked prior to powder coating ...
And if you are using a fuse holder not integrated in the IEC inlet, make sure it's wired in the correct polarity ! If the user tries changing the fuse with the mains cable plugged in, the live becomes exposed.