Originally posted by Urnamaster13 i thought of Manual flashes as i assumed they would be cheaper and useful to learn flash usage. Is that a wrong assumption ?
I will be using this flash on a K-500, with no plans to upgrade the body till next 2-3 years.
It really depends on how you go about the learning, and what photographic situations you want to be shooting in ....
If you are into experimenting, and are interested in light balancing and creating effects of depth and shadows (in other words, creative lighting), then there's a world of study and discovery, and a Fully Manual radio triggered system of flashes (eg Yongnuo or Cactus) is ideal.
If you need to photograph with a flash on the camera, because of space limitations, or moving around dynamically in an event, chasing after subjects like kids and people at parties etc, then a P-TTL flash is the way to go. All the great points made by others above are relevant. You can still light creatively with automatic flash exposures from the camera, by using bounce and diffusion, flagging etc techniques. And your P-TTL flash can come off the camera and be triggered by your camera built-in flash (no further equipment needed) for even better lighting angles and effects.
An off camera Dedicated system flash can be set to Manual mode and triggered by the on-camera 'P-TTL' built-in flash, so you can still get full and precise control over the power off-camera. Or use it automatically if the subjects are moving around a bit and your distances keep changing.
On-camera P-TTL High Speed Sync flash is a great way to create photos with pop and grab control over the lighting balance in bright outdoors situations.