[Diffusion]

I currently own a Sunpak 383 all manual flash. I occasionally use it with a home-made diffuser, often as a bounce flash, and lately rarely altogether.
I looked through some pictures yesterday, and I found that I got some pretty good pictures in the past with it (shooting in auto-mode), but occasionally got some bad shadows when I did not pay attention. (Which I often do, more of a snap shotter some times).

So, I have a couple of questions:

a) Is there a fundamental disadvantages of diffuser vs. bounce, other than the reduced range - which is not an issue for me?

b) I usually need to dial-in the exposure to get correct results with the flash in auto-mode (a couple of test shots, then I am good to go, as long as lighting does not change). Theoretically, this should be easier with P-TTL. Is it?

c) While the Metz 58 looks very nice (auto-mode that reads the camera settings), the Sigma EF-530 DG Super or the Metz 48 would probably suffice for me. Does the Sigma have a similar auto mode as the Metz 58. I know the 48 does not.

d) Is there a flash gun that deals best with diffuser P-TTL?

I did consider getting cactus triggers or similar to move the flash off of the hotshoe, but I really do not use studio-type setups. Any " easier" solution to getting the flash off of the hot shoe? Is it possible to get a P-TTL cable where you can put the flash on and off the hot shoe while the cable stays connected? To give you ideal flexibility?

Thanks,

D.