--The Amperex tubes have more top end attack. I wouldn't call it bite. There's more detail on top....not much, but it's there.Your observations are spot on. If these tubes are new, they will require a burn-in period.
--The Amperex may be less warm. The bass seems to be more defined but there's less of it.
--The Primaluna's sounded a bit bloatier, which was kind of nice in some ways, yet in another it's making me thing and digest these differences.
--While the soundstage of the Amperex seems to go back deeper than the Primaluna, it seems like I'm sitting a bit farther back from the performance. I cannot tell which I prefer.
The Amperex do indeed have more air and detail on top. They are not a warm tube, but should sound full-bodied. I have never owned the orange label Amperex, but their Holland factory tubes have deep bass extension so maybe your's need more time.
Wide, deep soundstaging is what these tubes are all about. Hopefully, you'll like their spacious presentation. If you do, in the future look for the "Bugle Boy" version which are their top of the line tubes.