The Hall is one of Dapol's better steam locos. It runs quieter after many hours use. The down sides, as with other Dapol steam locos is the fragile rods, tender to loco wires and cardan shaft. The bent running board can be straightened by careful gluing and wobbles can be the fault of traction tyres which can be replaced. After weathering and the addition of a crew, they can look really good and they have a good slow speed.
As for the new 9F, there seems to be a lot of confusion over it's specs and it does seem to suffer from the wavy coupling rods issue that can occur where all wheels are driven by gears. I only have the older versions.
Dapol's smoothest steam loco is the Schools. It is a lovely looking model but has the same issues as the Hall mentioned above; It is however, very quiet.
Ian.