On a capped convertible point 5 is completely negated.
Point 4 is not relevant. Since preferred comes first any way.
Point 3 is a reason to do convertible note.
Point 2 is a good point. But you really don't want to be negotiating terms on Series A (which are complex) with an angel that does not deal with them every day. If the angel is willing to just accept what you give them then maybe that is a valid point against doing a convertible.
Point 1. At least at the time of raising the convertible note it costs about 10th of the lawyer cost as a series A. Maybe the lawyer cost is higher when converting it, but presumably you care less about lawyer costs at that stage.
