The only humidor I have with a magnetic fastener is one of my travel humidors (a Nat Sherman made by Mastro de Paja). The fit and finish of this humidor has never been great, but, the magnet does what it's supposed to, which is keep the lid from swinging open by itself.
I have several humidors with lock and key mechanisms, and sometimes the alignment can be problematic depending on atmospheric humidity. I would be more concerned with the fit of the lid to the base of the humidor. Is it a requirement to be able to lock the humidor? Kids? Friends that have light fingers? More often than not, I don't bother using the keys with my humidors; easy access is preferable. Aesthetically, I loved the Ambiente humidors I had by Daniel Marshall in the early '90s without locks. The clean, black lines and curves with no gold to disturb the simple visual was very appealing. Unfortunately, he hadn't yet figured out how to keep the humidification devices from bubbling his finishes and I had to return them all.
In my experience being a cigar smoker since the early '90s, a good wooden humidor makes a big difference in storage and melding and enhancement of flavours over a Tupperdore (mainly because of the cedar lining). I gifted a friend with a humidor recently and he was surprised and amazed how much better his cigars tasted than the ones from his Tupperdore (he did a test using identical cigars in each).