Hello,
Smock for me, I like trying out clothing for fishing and hill walking. The best I have is also the least expensive......Made in Finland the Varusteleka Sarma smock, £70 and is some bit of kit. Base layer under it and your never too hot or too cold. It is also comfortable under chest waders being a soft kind of polycotton / canvas material.
If you want to make it waterproof and still breathable, then wash it in some of the Nikwax Cotton Proof that goes in the washing machine, costs £10.
Other favourites I have are my Buffalo Systems Smock, or if it is torrential I have a posh Paramo which at the price I don't like to take fishing......in case of a wayward hook!
Steven