I have both 10" and 14" .30H barrels - the Super14 is for silhouettes and the 10" is for hunting. While I prefer the 14-15" barrels for cartridges like my .300 Savage or .35 Remington, the 10" is about right for lesser cases like the Herretts, .300 Whisper, .357 Max and .45 LC. The Herretts were designed for 10" barrels anyway.
Unless you want to shoot only light bullets ( <150grains ) you may want to specify a 10" twist. This will stabilize bullets over 200 grains yet give very fine accuracy with the lighter bullets. Many .30 Herretts were built with 14" twist rates with the original 110-grain bullets the case was designed for in mind.
I prefer the Contender in ths cartridge. It is smaller and lighter than the Encore for field use, and it is plenty strong for the Herretts. But either is good! :-)