I'm trying to decide which should I use. Both can inherit contextual filters, so in my case both of them are good solutions. Except that I already have the other view that I want to put together with the first, so with Attachment I would have to redo the whole other view as a new display of the first, but with View area I could just reuse the other view.
What is the concept behind them? Are there other differences than what I noted above?
Background: View is a view, a view can have many displays, such as page, feed, attachment, block.
With Attachment display, you can attached one display of a view to another display. A good video demo can be found by Doug Vann (its a drupal 6 demo, that can relate to drupal 7).
With Global: View area (Drupal 7 only) you can add a view inside a view header or footer.
This is no huge pro/con of doing it one way over another. The only thing I can think of is templating a view and styling it. There will be different html tags and classes for you to style.
As iStryker says, attachments allow you to attach one display of a view to another display of the same view.
Using Global: View area allows you to attach a display of another view altogether. This can be useful if the two views are not compatible.
For example, if you want a view of taxonomy terms attached to a view of nodes.
Global: View area supersede using Attachments? Why does Drupal always seem to provide you with 10 different ways to do exactly the same thing? I don't know if I'm confused but;
I can use pagination of the host view without any problems if I attach another view in it (header or footer) but the pagination isn't available if I embed another view's block or page into header (or footer) so it's a big difference to me...
