canon flashgun

Looking for a flashgun for a Canon 20d. Would like to know how Metz and
Sigma compare with Canon apart from the price
Thanks
John UK

I have a 20D and a 'Metz 54MZ4 for Canon' (comes with 3102 M3 SCA
adapter) I have found that under ETTL control, the Metz flash is spot
on target for exposure even with FEC=0, unlike trying to use the Canon
flash (which requires FEC +2/3 for correct exposure when flash is main
source of light in the shot). I much prefer having a flash unit with
reliability of Metz' Auto mode, as backup alternative to ETTL mode.

Interestingly, the Metz relies upon its own in-head sensor for ETTL,
rather than relying upon the Canon in-body flash sensor. So in truth,
Metz ETTL mode is not 'thru the lens' because they could get no
assistance from Canon in engineering a flash truly compatible with
ETTL. I think the upside of using its own in-head sensor is that the
Metz is accurate whereas the Canon has to compensated! Since I already
had Quantum batteries to speed the recycle of my Metz 45CT (for true
TTL with my medium format film camera),

The downside of in-head sensor is that you CANNOT use the Metz 54MZ in
a softbox when using ETTL...you must use Auto mode anytime you want to
use a softbox. Given the fact that 54MZ ETTL is not truly 'thru the
lens' and neither is the Auto mode 'thru the lens' , I suppose it is
somewhat immaterial which mode you put the flash into when you want to
use a softbox!

The various other features supported by Canon 580 are also available in
the Metz 54MZ...auto on, auto zoom head, focus flash, HSS, etc.