Nice looking town, lovely part of the country, but there is nothing going on. the tesco and aldi have pretty much killed off the local shops. the town needs an injection of life/money.
Builth is more old school farming town. Nice but mental on a saturday night, especially if you are English/not local.
Rhayader would get my vote out of the 3, more tourist focused, but not touristy. Slightly nearer a big town. Have looked at moving there when the kids have finished school.
I’d look west of Shrewsbury (well i did), I used to live west of Oswestry, and once you when over the boarder the house prices fell like a stone. But people are catching on.