The cons:
Mech mods require more in-depth knowledge about battery safety, Ohm's Law, and other key important battery safety related guidelines that are part the same (basic part), part different (advanced part) compared to regulated mods. Mech mods also require more advanced knowledge about battery performance aspects and about how these aspects relate to how a given coil build will perform. Getting the desired level of performance may prove to be a real challenge, and, performance also is limited, to a fairly large degree, by personal first-hand experience with, and technical knowledge about, coil building and advanced coil building. Mech mods are not for everyone. They are intended to be used by advanced users only.
The pros:
Mech mods have a great potential to give you a much better vape experience compared to regulated mods, i.e., they offer a unique opportunity to find out for yourself what all the fuss is about. Even, if you still end up disliking mech mods, at least you will no longer be able to blame it on yourself the fact you never did anything to try to find out what exactly your own preferences truly are. It's a new adventure, an exploration. To some (myself included), mech mods have become a way of life. Speaking of potential, mech mods also give the potential to be safer. That's because they give you more of an incentive to learn about fact-based safety, whereas regulated mods can, and very often do, create a false sense of security by letting the user wrongfully assume that the built-in protection features of a regulated mod logically imply they're safe, when the reality is that many people use these features for a pretext to not needing to learn about battery safety, and about common false myths surrounding battery safety. Also it's because I trust my brain more than I trust some vague Chinese chipmaker. Finally, mech mods don't break easily, whereas with electronics it is merely a question of time before it fails, and so I don't need to carry a spare mech around with me everywhere I go.