I'm 6'2", 35ish inseam running an XL HD. Now that I've ridden an XL Bronson and TBLT a bunch, I definitely prefer the longer fit of SC, measured about 15mm longer in reach. I'd be weary at 6'4" going with an XL Ibis.
Thank you for the first hand information. The Nomad isn't exactly long up top so the HD-R's numbers are a tad surprising.