Hello, couple days late but, figured I would chime in on this one.
There are several issues that can arise with the mail to link. Its not compatible with every mail client for start, I couldn’t imagine testing a link in every mail client, bet there are a few, most will typically launch the client, typically something gets left out, maybe the subject in Outlook, or Cc in Gmail, Thunder Bird, whatever.
A form sends those variables (message, subject, to) via a POST request, its far safer because its not stored in the browser cache, what if the message contained privileged info, anybody can see it .
And lastly, this is my favorite btw, browser bots, more so email harvesting, its an awesome way to get spam, junk, malicious material, and once one gets that address, its for sale. Almost ruin an email account.
Anyways, to each is own, they both work, but thats why forms are the industry standard. Cheers!