I have the Verlinden 1/48 scribing templates. The work very well, are very flexible and there are many shapes on the templates.
I recently scribed some panels onto some fuel tanks for a 1/48 F-15 I'm working on. They turned out great! Just secure the template on the surface with some tape and you're good to go.
These are the only templates I've used so I can't compare them to any others.