It will be interesting to see what you have to say about ELIZABETH & ESSEX. A few years ago, I had made a disc of ELIZABETH & ESSEX and THE VIRGIN QUEEN which I called 'Bette Davis as Elizabeth I' then gave it to a friend of mine to watch. A week later she told me that as much as she loves Flynn, she preferred the second film. Her feelings seemed to echo mine.
Obviously, both films are big-budget affairs, given the proper treatment by the respective studios (Warners and Fox). But I feel Fox's VIRGIN QUEEN comes out ahead, because the editing is tighter, and the script has more layers embedded in it. Meanwhile, Warners' ELIZABETH & ESSEX relies a great deal on Korngold's score, the lush Technicolor and the personalities of the two leads-- at the expense of complexity and pacing.
Another thing I think the Fox film does better is how the 'other woman' (Joan Collins) is much more fleshed out. In the first version, Olivia de Havilland is absent for a large portion of the action and only turns up at key points. Perhaps this is because Warners saw their tale as a Davis-Flynn vehicle and only squeezed de Havilland into it when she had days off from Selznick on GONE WITH THE WIND. But over at Fox, we have Davis at a point in her career where she was a freelancer and not really a studio property. Clearly, Fox was more interested in building up their ingenue Collins as a brunette Monroe, or as their very own Liz Taylor type. So they made sure that while Bette's character remains important that she is not the sole focus and the narrative can be turned over to Collins at periodic intervals. And I think Collins shines with this opportunity. She works well with Richard Todd, as does Bette. Todd is a much more classically trained actor than Flynn, which helps with this kind of material, that can otherwise become stodgy.
But getting back to what you said, Ian-- I think that when you have the chance to watch the earlier film, you may find it a bit jarring. Why? Because it is obviously Bette quite younger in old woman's make-up. So the artifice is easier to notice and despite her stellar performance (she is equally adept in both productions), she lacks a maturity in 1939 that she has in 1955, which if you think about it, playing an older woman really requires.
I also predict you will consider ELIZABETH & ESSEX to be somewhat slower, because there is less action and a lot more talking heads, which makes it drag in spots. Of course, this issue could have been fixed with editing and with a script that played up the various court intrigues. At Fox, they played up the supporting roles and eliminated extra scenes that bogged the story down. But at Warners, they were playing up the spectacle and pageantry in costume drama, so they let it go on and on and on.