I have taken both ships and enjoyed them both as well. The Queen Mary 2 is a classic Ocean liner and if you are a ship buff (you seem to be) then you will really enjoy the experience onboard.
But I really recommend the transatlantic on the Queen Mary 2 - I think this is a trip every cruise should take art least once.
You cross in 6 days - almost as fast as the heyday of ocean liners, and the entirwe trip is like a journey through time because of the extensive lectures onboard about Cunard lore and history and the history of ocean liners.
The Queen Victoria is better for port-intensive cruises. It is a beautiful, smaller ship similar to Holland Americas newer ships in many ways. The food is very good on both ships. If you are thinking of a crossing, I would definitely take QM2, though.
I guess I could sum it up this way - you will love both ships, but the QM2 is a one of a kind in the world ship, while the QV is more of a standrad cruise ship - but of very high quality. Base your decision on which you are more interested in - the ship (QM2) or the ports (QV).
As for Queen Elizabeth - I don't know enough about her yet. I have get cracking on that!