The most powerful meditations that I've had with a Tarot deck have been with Tarot of the Spirit. The artwork is abstract and I found myself going into deep meditations to connect with it. It took some time, even though I am used to meditation but the results that I received have helped me to understand the deck. For me it the deck is more useful in this way then for reading with.
I find that Thoth based decks and the Thoth deck itself seem to give me good meditations. RWS decks don't do that in the same way as I already have pre-conceived knowledge of the meanings and this influences what I am trying to find out for myself.
Marseilles decks also give me good meditations but in a different way, they send me off in search for answers and I end up with many tabs open on my computer and reading loads! But I take alot of notice of faces and expressions in Marseilles decks, they seem to tell me all about the people, their viewpoints and their emotions... sometimes this takes the place of the generally accepted meaning for the card.