I have both, too, and I agree that you should buy both ;-)
The Touchstone has much more well-known art. Most people know little Early Renaissance art, like used in the Golden, but the artists in the Touchstone (Rubens, Holbein, Giorgione, Bronzino, Caravaggio, Titian...) are very famous. I find Kat Black did a great job and the knowledge of the original doesn't interfere in this deck, the way it did for me in the Art of Life tarot and sometimes even in the Botticelli, but others may be irritated. So the Golden is a safer bet if you don't want to see the image "fall apart" because you recognize each of the persons and from which paintings they were taken.
The Golden follows the visual formula of the RWS closely; in the Sun for my taste too closely. The Golden gives you full scenes, the Touchstone gives you close-ups of faces. In the language of art history, the Golden shows genre paintings, the Touchstone portraits. The Golden gives you scenes to read and interpret, the Touchstone gives you facial expressions.
The Golden is lighter in colour and cooler; the Touchstone has a lot of brown. Early Renaissance art is much flatter and figures are organized on a frieze or stage, very much like the RWS. Late Renaissance, Mannerism and Baroque art plays with depth, strong contrasts of light and shadow, and more saturated colours. You might find yourself preferring one over the other (I don't, I find each visual language interesting).
Kat Black did a very good job in blending the images, but sometimes you can see "seams". You can see that the Touchstone is her second deck: it's IMO more skillfully done, with more attention to light and shadow (if you don't have a common light source, your eye will notice there's something "wrong" even if you couldn't identify what's making you doubt the integrity of the picture) and with a stronger colour scheme. Cups give you blue, Wands red etc - strong patches of nearly undiluted colour that unite a suit visually.
But the cooler, more distant and less identifiable suit-oriented coloring of the Golden is lovely, too.
No, I can't decide, and I wouldn't wish to be without either. I use the Touchstone more often but love the Golden very much, too.
You'll be able to read each of them out of the box. They're a pleasure to behold. They come in beautiful, solid boxes. The booklets are well done. These are tarot decks that are meant for tarot readers, not for art collectors, in spite of their art origins. And they make you feel special, well, at least me. There's a strong positive energy in Kat Black's work, a Queen/Wands energy, something that inspires good readings.
That's my completely subjective point of view.
ETA: Golden Tarot is Florence and Flanders - Touchstone is Venice and Fontainebleau. How can you choose?
you won't regret it.
