Let's first have a look at the dry leaves. On top, the 1975 plantation pu er are buds and are much smaller than the wild grown leaves from Jiang Cheng. They also look pale and a little bit grey compared to the darker, sharper color. We'll see later how to interpret the color.
Let's now have a look at the color of the infusions. 1975 is left and 1990 is right. We have to focus on the small cups, because for the large cups I used more leaves for the 1990 than for the 1975 (that's when a scale for grams would come handy). I corrected this difference for the 3rd brew. We see that the colors of both teas are quite similar and produce very beautiful shades, which vary according to the infusion time.
The open leaves are easy to distinguish: the big ones are from Jiang Cheng and the smaller buds are from 1975. Both leaves turn brown and the 1990 even displays some greenish leaves. Here we can confirm that both are raw pu er, slowly aged.
The major difference between them comes from the intensity of their taste. The wild pu er is true to its nature: untamed and powerful. It displays a broad range of wood, wet forrest, sweet nuts... The cha chi is very strong and you feel your mouth being massaged (kissed!) for a good minute. The 1975 plantation pu er was much smoother to the palate, but also weaker in comparison. It lacked the strength in terms of flavors and cha chi of the 1990. 30 years have rounded it beautifully, but it was like going to a small classic concerto after listening to a performance by David Bowie or Led Zep.
In terms of pleasure, I give them the same rating. To taste a 1975 puerh made of finest tea buds is a fine pleasure (like a few real caviar eggs on a hot toast). The 1990 displays more intensity in everything and shows enormous potential to taste much better than the 1975 in a few years. And since the 1990 Jiang Cheng wild Puerh is more than half cheaper than the 1975 Jin Gua Gong, it's a much better value. That's the reason why I didn't select it in my list of teas. Not because it's not good. It's just not good enough compared to the wild pu er brick.