Rally boys use open face for a few reasons but mostly because they spend most the time looking out of the side windows so need a larger field vision.
I've got a Bell full face which has a visor and a sunstrip that you can interchange, they are pricey though and mine has a HANS device as I use it for competition. You won't need all the FIA gubbins but if you can stretch to one I highly recommend them. Soo comfy and fit really well.
For track days I would get a full face and replace the visor with a sun strip so you don't get double glare off the windscreen and visor. Even in a caged stripped race car you can still get hit in the face by debris, in a road/track car, although unlikely the risk is there. You only get one head.