Honestly, I find AF-problems with UWA lenses basically a non issue.
That is because in most of the cases you can safely focus manually
with excellent results. Ultra wide is not easy for the AF system, since
for a certain change on the focus ring, there is not much change at all
on the AF sensors (on the tele side, the situation is just the opposite).
That's why I usually do not rely on AF at all when using an UWA lens.
Between two UWAs, one with correct AF and slight decentering, and
one with AF slightly off and no decentering, I would always prefer the
one without decentering. But what works for me might not work for you.
Just my toughts ... Rainer
That is because in most of the cases you can safely focus manually
with excellent results. Ultra wide is not easy for the AF system, since
for a certain change on the focus ring, there is not much change at all
on the AF sensors (on the tele side, the situation is just the opposite).
That's why I usually do not rely on AF at all when using an UWA lens.
Between two UWAs, one with correct AF and slight decentering, and
one with AF slightly off and no decentering, I would always prefer the
one without decentering. But what works for me might not work for you.
Just my toughts ... Rainer