Go for the Isonic, you will not regret it !!!
As Mark H said, you are an experienced windsurfer and will have no problem to handle these boards.
They are superfast and easy to sail.
I started on a 170 liter Starboard Go. After 3 seasons I jumped to a 145 liter Isonic (1/2 season), then 122 (1,5 season) and now 127.