The helmet speakers are great for commutation at lower speeds .... Behind the great big windshield of the Harley. In the wide open expanses at higher speeds ear buds are the way to go.
If you want to take it to the next level, get "EarFit" ear buds... Not cheap, but it's like sitting in a sound studio at all speeds... I found with over the counter ear buds, the sound level on my iPod would have to be set at 60 to 70%, with speakers at a 100% and with EarFits the volume never has to go above 30%.
There are apparently really quite helmets out there bring down the noise level substantially, but well over $600, so that's an area I would not be able to comment on.
2015 R1200GS, 2009 WR250R, 2006 Super Sherpa, 1978 XS650 Special, 1978 KE100, 1967 CD125A, 2004 BWS. ROKstraps Dealer