re: Conclusion - Which is the best IMO

Definitely shooting for using straight grain stock cutting to finished size yields the highest degree of success forming nice dowel. 
While it's not always possible it should be a primary pursuit for best results. 
Keep in mind the latitude of this topic depends on what the dowel is being used for in your project. You can still form dowel with not so straight grain available and get what you need for dowel joinery. But the importance of straight grain may be required let's say if you are doing hinges.