Revell makes a 1:72 kit of the 80 foot ELCO. It is currently sold as the PT-109 and has been previously sold as PT-117. It is a very nice kit and can be made into a very nice represenation. There are some minor problems with it (scribed decks) which can be lived with or corrected. There may also be some sink marks. The kit is 40+ years old and may show some of its age. It can be found for 10 dollars or less
Even older is Revell's current re-release of their PT212. It is not 1:72 scale, something entirely off the wall. Its also represents another class of PTs than the ELCOs. The molds are probably 50+ years old and are very dated. The crew are molded integrally with the guns. The guns are poor - one looks like an old movie camera. It makes a good bathtub toy. Revell was trying to ride the nostalgia train.
The Italieri PT is big. It is in 1:35 scale, or roughly twice the length of the 1:72 kit. It is a late-war version of the 80 foot ELCO. It will be more expensive than the Revell 1:72 scale offering, probably on the order of a hundred dollars. It can be made into a very nice and impressive model, but it is big (display space) and daunting (expense if I screw it up). I wouldn't consider building the Italieri kit until I had several complex armor kits under my belt.
If you are a relative NOOB, I'd consdier the Revell 1:72 scale kit. You can see elsewhere on this page what can be done with it. Later as your skills grow you can add aftermarket items to complete the details which are soft or lacking onthe Revell