merthyr has a large sourounding area which is nice.
i have spent a lot of time in pembrokeshire and find it pretty boring compared to south/east wales. plus plenty more riding south/east and the people are more friendly this way too.
i would say pembroke is a place you would retire too.
look at places close to merthyr like pontypridd,blackwood,aberdare,caerphilly,machen, tredegar a good estate agent is peter alan.