A lot depends on the size of the figures, the numbers on each base and the thickness & type of the base material.
If you have multiple 28mm figures on large, thick bases then the button magnets are a good solution but sheet magnet (0.8mm thick is best) on the bottom of the base will give more than adequate hold for heavy figures on a large base.
Single, heavy figures may need a button magnet, particularly if the weight is high up.
15mm & down and on multi-figure bases – magnetic sheet is adequate (even 6mm thick usually works OK) for any but large figures or mechs that are top heavy and on smallish bases – use buttons for those too – or give them larger bases.
The magnetically receptive material that you store them on is also a factor in the strength of the magnetic grip. A soft iron impregnated vinyl sheet (like Ferrosheet) stuck to a flat surface is good enough for most purposes but a thin iron sheet is better.
I use metal drawer filing cabinets for storage and figures are moved around the house in those. I also have plastic trays lined with Ferrosheet for when I take them elsewhere. So far no damage but I am careful !!!
Last point to bear in mind is that a sudden blow will most likely jolt some figures off the storage unless there is a good area in contact with the magnetic base. Adding a bit of bubble wrap above the figures will at least reduce damage if you happen to drop them.
Tony of TTT