Using simul is a perfectly fine way to generate IRFs in the presence of OBCs (if it works). It allows you to capture the full non-linearity of the model, under perfect foresight. If I’m asked to referee a paper that doesn’t estimate a model, and only ever shows IRFs under a first order approximation, then I’ll always ask them to replace the IRFs with ones from a “simul” type perfect foresight approximation, which should at least dominate the first order approximation.
The main difficulty is that simul’s perfect foresight solver will sometimes struggle to find a solution, particularly in the presence of OBCs. DynareOBC is guaranteed to find a solution if one exists. Additionally it lets you approximate the rest of the model at second or third order, to capture other non-linearities, and it can also capture precautionary effects of the bound.