For me it's a question of how much I get out of a card. When I started out I used things like the RWS and Morgan-Greer. However, when I began to study Kabbalah and other things like that, I found that the whole intuitive reading thing remained, but that my knowledge and understanding of a given card was deepened and expanded. So I gained a lot without losing anything. Of course, it is always a question of what's "good" vs. "good enough." Sure, beginners' decks are perfectly serviceable, but adding structure and symbolism to the mix allows you to go much further, to find connections between cards and their ideas, being able to see the deck as a unified model and understanding all its excesses and balances. Going strictly by the images just doesn't give you that to that extent.
The chief advantage of more abstract decks is that they allow you to better distill the card's essence, being able to then apply it to any situation since you're constructing the meaning out of several different sources and arriving at as pure an idea as possible. It also helps maintain objectivity because of external constraints and balances that allow you to take the reading out of yourself. You not only know what a card means in ways that surpass LWBs or simple personal interpretation, but you also know why it means what it means, and how it connects to other cards in the reading and how it behaves.