I would have to agree with Helmut on this.
As others, I find findagrave a useful place to start, but that's it.
Honestly, I don't understand the motivation to update all these various sites. Why have family trees in multiple web sites? Why have gravestone / marker pictures in multiple sites?
This is what I like about WikiTree, is that it can all be done here, in one place.
Yes, it takes more effort to actually do the work here. But I like the focus on a single tree, the collaboration involved, and the idea of continuous improvement towards greater, and greater accuracy over time.
I would much rather spend my limited time and energy in ONE place that has the ability to do everything. I would rather we campaign to get the people who use Find A Grave to come here, and upload pictures here!
And if those people like having memorials, well then figure out an easy way to make memorials here.
It's better if we can get more people to collaborate in one place, than to split time and energy and collaborate in multiple places, with duplicated information.