Whichever fit better. I haven't tried the Giro, the Kask has a weird padding layout that feels unusual on the front of the head.
In terms of performance it's probably so close and so personal that it doesn't matter.
In terms of style I reckon the Grio looks like a box...
Both were on my shopping list and I ended up getting a Lazer. And the Genesis not the Bullet, because their own reported aero differences were miniscule.

Neither.

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Swimming Workout of the Day:

Favourite Swim Sets:

2020 National Masters Champion - M50-54 - 50m Butterfly

Did you know that some people say that I'm not helpful?

I've raced a few times in a Vanquish and really like it, very comfortable, great quality lens.
That said, it could be a total aero brick for all I know.

Some have said that ;-).

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Swimming Workout of the Day:

Favourite Swim Sets:

2020 National Masters Champion - M50-54 - 50m Butterfly

Noooo! Really?
When you're here day in day out sharing gems like this?

I pretty much agree. The Vanquish is a very nice helmet. I was doing a bunch of 8 mile TTs for training this summer using the Vanquish. One day I brought out the Aerohead and mowed 30 seconds off my best time at about the same wattage. Some people are close to as fast in an aero road helmet, i am not one of them.

I actually bought the vanquish so that's what I'd buy.

That said, I time trial with the aerohead :p

If you can't decide I'd go for the vanquish, simply because it has MIPs (and anything that might protect my noggin better is appreciated)
Also know a few people with vanquish's that seem really happy with them.

Vanquish especially if you're worried about the heat.

Aerohead is faster but it can become an oven in hot races

I'd also buy neither.

When going for a road helmet I went for the Lazer G1. If I want aero I'm buying a full on aero helmet and not something halfway inbetween.

Can confirm.
I love my Utopia, except for the front pads. I get funny marks on my forehead and have to be careful about it being too tight.

[/quote]

Vanquish especially if you're worried about the heat.

Aerohead is faster but it can become an oven in hot races[/quote]
This is a great article by AeroGeeks regarding the Vanquish. http://aerogeeks.com/...anquish-mips-review/
It doesn't compare the Utopia & Vanquish but gives a good review of the Vanquish and compares it to the Aerohead. I've got a Vanquish and have been very happy with the aero qualities & cooling effects.