It’s really about how the helmet fits. If the Giro is comfortable, I’d stick with it. If it’s not, try a Rudy.
The Rudy Actyum is incredibly well vented. It sits high on some people’s heads, though (like me). The Bell Volt (which is practically the same thing as the Giro Ionos, and I know I will get in trouble for saying that by fellow STers) is MINT. It’s cheaper than the Ionos and has a slightly different shape, but I actually like the ratchet system on the Bell Volt better than both Rudy and Giro because it stays tight for long rides on crappy roads (my only complaint about the Rudy is that it loosens up and then moves around on my head, but I can’t go down a smaller size because a smaller size doesn’t fit).