I biased, but France, of course! lol
Lots of trails, barns, and if you pick your area correctly, great weather.
Portugal! Never been but have friends who did and loved it. And those Iberic horses and classical dressage! AND decent weather.
I’ve always wanted to go to NZ for a visit. But getting approved to live there might be tricky? I don’t know.
England / Scotland/ Holland might be great horsewise but the weather would be so depressing to me. I don’t do well with rain rain rain for days on end. Although I was lucky to spend a week in Belgium/Holland in the summer and we had gorgeous weather!