I'll make this blog entry short and sweet. These are my personal Pros and Cons

Pros of using SFM:

• All of the models and props are presented to you right at the get go.
  
• Camera and lightning are easy to work with
  
• No need to use 2 or 3 other programs for special effects.
  
• Posing is easier
  

Cons of using SFM:

• Want a specific model or prop that would make a scene 50x better and no one else thought of this? Too bad.
  
• Pose to pose can be a giant pain, especially a lot of movement
  
• Sometimes the presented maps are not good enough for certain scenes
  

Pros of using Adobe Flash:

• You draw everything
  
• Pose to pose is easier
  
• You don't have to render everything to see the complete project
  
• It's the #1 2D animation program
  

Cons of using Adobe Flash:

• My drawing skills are TERRIBLE
  
• A lot of work just to make a line look perfect
  
• Camera work is kind of a pain
  
• Interface is very odd
  

I have experience in both SFM and Flash, but I would go with SFM every time. I know there are Pony Puppets for Flash so a person wouldn't need to draw anything but if I wanted to make something non pony related, I'm up a creek without a paddle.

That's my personal outlook on those two.