Good reasoning is invaluable; it's what philosophy is all about. But I'm more skeptical of formal logic's value. Logic is a powerful tool we can use to structure our reasoning and highlight entailment relations. But - like any tool - it can be misused. In particular, I worry that it's just too easy for the manipulation of symbols to substitute for careful thought.
Modal logic is especially susceptible to misapplication, in my experience. The most famous example would have to be the S5 modal argument for God's existence. But it's also not uncommon to come across blog posts where the employed logical apparatus merely serves to build in misunderstandings. The formal steps of the argument may be flawless, but that's all for naught if the entire argument is based on a mistake -- due to failing to understand precisely what all those formalisms really mean.
If one opts to engage in formalism, the hard (philosophical) work lies in interpretation, i.e. ensuring that the formalism adequately captures the intuitive ideas we started with. It's easy to neglect this point, and so produce a formal 'proof' that doesn't really speak to the issue at hand. That's the risk of formalism. The advantages are more well known: they force us to make explicit intermediate steps in our reasoning, and allow these to be easily checked for validity. Do the risks or benefits tend to be greater in practice, do you think?
My tentative (and admittedly under-informed) opinion is that logical formalisms are rarely indispensible, and often well dispensed with. As a rule of thumb, I'd be wary of using formalisms as the central means of making your case. Their best use may instead be to provide a bare-bones outline of the argument's structure, as a supplement to the argument given in prose. Formalism may prove helpful, but it shouldn't be considered sufficient, since there is more to good reasoning than logic alone.