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Between those two, I'd go with StamDK for PvE because it has no clunky cast time/channeled abilities and feels more fluid than Templar (though Templar generally has better sustain). You can always switch to a tank for group content too since the class is very much suited for that. For PvP, StamDK for sure -- It's my main after all. It's just an awesome class in PvP, especially Battlegrounds.
For solo play you can replace stamplar with literally anything else and it would do better.
Both stamDK and stamsorc are ideal for beginners in different ways. But they also don't offer a lot of flexibility in playstyle, you have to use mostly weapon skills.