I'd say France but that's probably because I took early retirement last year, and moved to a village near Limoges at the tail end of last year.
Yes you need income, either your pension or private pensions or rental from a house or investments.
Yes you need private medical insurance for the first year for your visa, but we got into the French system which pays for 80% of medical bills 6 months after getting here.
The weather is quite variable, but it is always warmer here, the veg grows quicker, there is less time being so cold and damp, but on the other hand some days it is too hot to do anything.
It all depends on what you want really, flights are weekly from some airports all winter and stop altogether from other UK airports and only start up again in June. We live in a village that is owned by 60% Brits, who come and go often staying 2-3 weeks only. It's more usual to hear British voices here, in the middle of nowhere, than French. There are no buses at all, and you have to drive everywhere but the house was half the cost of our UK house and twice the size.
The cost of housing is more expensive by the sea and coastal towns are mostly quite well kept unlike the UK. There has seen a larger contingent of city types moving out of the cities here, partly to do with COVID and new types of working arrangements.
My recommendation is to visit in mid winter. If you still love it then, it more likely you won't hate it if you move there.