While not an expert, I have hunted three areas in Moz, three areas in Zambia, two areas in TZ and have another trip booked for two areas in TZ in 2027 for my son and a friend.
All are diverse. In northern Moz in the Niassa Reserve, you can hunt essentially the same animals as the the Selous in TZ for less money but now the terrorism there in northern Moz has caused problems. Many safaris there have been cancelled. In eastern Moz, the delta is very good, although the buffalo genetics there are a bit smaller. I have hunted the Niassa Reserve, the areas around Lake Cahora Bassa and Coutada 9. I enjoyed the Niassa and C9 the most. I've never hunted the delta but it is known to be great as well with indigenous nyala and suni available.
Zambia is wonderful and contains unique indigenous plains game species there that are hard or impossible to get elsewhere - puku, sitatunga, three different lechwe, yellow-backed duiker, etc... In addition, Zambia has awesome big maned lions, large leopards and huge sable.
Tanzania is also known for unique indigenous plains game species such as sitatunga, lesser kudu, gerenuk, Grant's gazelle, Robert's gazelle, Thomson's gazelle, Coke's hartebeest, and great cat and buffalo hunting.
I love the different plains game species and that is what has led me to these countries more than once.
As for costs, the areas with the big dark maned lions bordering Kafue National Park (Kasonso Busanga, Lunga Busanga, etc..) in Zambia are surpassing the most expensive lion safari areas in Tanzania. I learned today that Fico Vidale is fully booked for 2026 & 2027 at $200k for a lion safari. Ouch!