Both are right. In the northern states and Canada, it can take full sun. Just make sure it can withstand your zone. I am not clear on the zones where it can be grown as some plant nurseries & universities claim Zone 4 while others (www.hydrangeashydrangeas.com & other nurseries) claim even Zone 2.

In the southern states, like Texas/Georgia/etc, it must have afternoon shade or the leaves will suffer from sunscald as summer approaches.

And yes, Annabelle probably would grow in full shade (if that is what you meant) but bloomage might suffer. The blooms may be smaller than normal or fewer; if planted in dense shade, the shrub may end up with nice dark green leaves and no blooms at all. However, I have never done that or heard of someone who has tried that with Annabelle.

I have them in two different locations where they got
a) 1 hour of direct afternoon sun + dappled shade the whole day,
and
b) 3 hours of very early morning sun + dense shade thereafter.

In both cases they bloom profusely with only one noticeable difference, in position b) they stay white for about 7-10 days longer than in a position a).

Thanks for the information "luis pr" and "ego45" I seem to have a few hours of direct sun late in the day in the spot i thinking about planting Annabelle in. So i'll try it and we'll see.
Mark..