As a Formula 18 group we are fotunate to be able to choose our boats based on lots of criteria, including manufacturer if we are so inclined, without worrying about which is better. This is a box rule class and the box is very successful. Meaning that most of the boats are equal around the course. I have sailed on my own and other's Tigers, Infusions, Nacra F18s. Even the Tigers were a bit different based on the character and preferences of the owners. All of the boats are different in feel and all the same in speed. It is astonishing that way.
Are you planning on buying a new boat or a used boat? We can all chime in a little more if we know. If you are buying an older boat there are some concerns that will have to be addressed depending on the boat. One big example it the Nacra I-18 was sold with a carbon mast which in no longer even grandfathered into being legal anymore.
Later,
Dan