I'm a big fan of Giraud especially for high volume 6mm cases like Dasher/BRA. You see very little case growth so assuming you trim every time it's more like a quick chamfer debur than any significant length trim. I'm loading for two shooters and working with well over 1000 cases at a time so overall speed is a big priority.
The video above shows trimming with the Giraud at around the 11:10 mark. You can actually go 25-50% faster than in the video by setting up your brass bins front to back (untrimmed brass in front of the trimmer, finished bin behind the trimmer) then using alternating left/right hands to feed the brass and toss into the bin.
I could see the Henderson being nicer for larger cases or cases where you are trimming off a bunch of length, easier to hold the cartridge with the collet than by hand.