I'm the same height as you and have both a Giro20 and a Strada. IMHO you might be better off with the 26. The learning curve is a little steeper but not by much.
The Giro 26 has a longer frame which will allow you to set the seat closer to the center of the frame. In my experience my Strada rides and handles better because I'm more centered on the frame. Even the my Giro20 has slightly wider tires (35mm vs. 28mm) the ride is better on the Strada. Also, the lightly weighted front tire bounces pretty hard on road imperfections.
The handling on the Giro is quicker. I don't know if its due to the unweighted front tire or the fact that its only 20".
If I were to do it all over again I probably would buy a Giro26 instead. Not that the 20 is bad but I think the 26 is a better fit for riders 6' and over.