I have a Sparco SN2000 model carbon-mix helmet with HANS anchors (SA2000), an open-face Bell (SA2000) for autocross/instructing, and a Pyrotect full face (SA2005). All fit differently and are all different sizes, but are used for different things. I find myself using the Sparco for karting and the Pyrotect for track days, and the open-face for everything else. I can always swap the HANS anchors to the Pyrotect helmet if I need to.
Zamps are nice, they are inexpensive but have good construction and are pretty light and have a good model range. lighter than the Pyrotect or Bell M2 model full face units. Probably the same weight as a G-Force full face, but I have never been impressed with their build quality nor fit.