We will be landing in San Jose on the 21st and have reservations in Monteverde on the 24th thus we have 3 nights to stay somewhere. We also have the desire to see a volcano other than Arenal (we've already got that planned for later).
So Irazu or Poas?
Poas is more in the "correct" direction and with a little bit of hunting I think it will be easier to combine one day around Poas with one day of rafting prior to heading to Monteverde. On the other hand one member of our party has mentioned that Poas has had some dangerous activity recently.