I shot one of those once and was very impressed. I figured it would pattern badly and have a lot of functional problems. They seem to be a great shotgun.
I would prefer the .45 ACP over the GAP. The GAP can't do anything better then the ACP, but the ACP can do more. Still, if you have smaller hands that is a good step up.
Me, I have fingers like sausages and huge hands. I like the old 1911 grips.
The 1911, no matter what the grip, just doesn't index or balance "right" in my hand. Unfortunately.
I tried the Hungarian ripoff of the BHP-DA in .45 ACP, the GKK-45. It balanced right, but was an enormous POS.
The Saiga is a high-quality AK, with all that that implies. The accuracy problem isn't a problem for a shotgun. :)