I've done both....both completely different experiences and depends what you are after.
Kyrgyzstan is horseback with spot and stalk. A bit lower elevation. Lots of glassing. Sheep are smaller and have different horn configuration. The capes in my opinion are more beautiful as more tan, brown in color. I stayed at a hunting lodge and also in a more remote "sheep herder" cabin as a "fly camp" where we packed in with horses to hunt areas not accessable from main lodge. Saw fewer sheep. Big ibex typically not in the same area where hunting sheep but certainly can get an opportunity at a representative species. Sheep will be more often than not, more representative of the species from a trophy standpoint. Sheep size will be in high 40's to lower 50 inches as common.
Tajikstan. Depends on where you hunt. I hunted northern part from Lake Karakul. Actually flew to Kyrgyzstan and drove across the Tajik border. More vehicle based hunting with spot and stalk leaving from the valley floors. Higher elevation and more remote. Sheep are bigger body and horns with capes having a lot more gray color tones. Saw a lot of sheep each day. A lot. Saw lots of ibex as well. Was able to take a larger than representative species in the same area hunting sheep. Sheep trophy size will be 56-57" on average. Sheep over 60" are harder to come by and often will have to pay additional trophy fee.
Both are cold, with Tajikistan being colder with avg temps being around -15 F.
Booking agents use the same local outfitters for the most part, especially for the the most popular hunting camps.
Both require proficiency at long range, 600 - 800 yards common (this is long range shooting for me)
Kyrgyzstan was about 1/2 cost of Tajikistan.
Kygryzstan felt more of a mountain hunt and better overall hunt experience.