VoIP wins for almost every small business now, but not for the reasons the ads say. Honest breakdown:
Where VoIP wins: price (roughly half the cost per line), features that copper physically can't do (ring your cell and desk together, voicemail arriving as email text, texting from your business number, menus without hardware), and flexibility, adding a line is a config change, not a truck roll. And the copper network is being retired anyway; carriers are raising analog prices on purpose to push people off. The choice is increasingly WHEN you move, not IF.
Where landlines still win: they work in a power outage without a battery, they're immune to your internet going down, and old equipment that speaks analog (elevators, fire panels, some alarms) needs them or an adapter. If your internet is genuinely unreliable, fix that first or keep a cellular backup, VoIP is only as good as the connection under it.
The practical answer for a small business: VoIP for your working lines, with the mobile app as automatic backup (if the office internet dies, calls just ring your cell, which is on a different network). Special-purpose analog devices get individual adapters or cellular units. That's the setup we install: modern where it helps, boring and reliable where it must be.