The 38 Citation is a nice sailing boat and an excellent value and fairly fast.
No...this is not a blue water boat and yes... she is fine for lake Michigan
I don't think Irwins are any better or worse than the other production boats of the era .
I have sailed both blue water and Lake Michigan and I can tell from experience that blue water sailing seems easier than LM with the exception that in LM you are always closer to a safe harbor. It is not unforeseen to have 9 ft waves on LM that are to close to ride them like you could in "blue water" 12' waves. Resulting in a pounding of your ship that must be build to withstand this.
Therefore if a boat is good for LM she is good for blue water (when equipped correctly)
I've sailed the North Sea off the NW cost of Europe and can tell you that, that small body of water is much worse than some big oceans. The same with the Great Lakes, a lot of large commercial vessels perished in these "timid" inland lakes. Don't under estimate them they similar to oceans only not as salty.