It's pretty easy actually but when authorizing GMail to add a new sender address it usually mails a verification code to that address. Which, in this case would come back into the same Gmail inbox.
So if you have a X@Y.Z forwarding to A@gmail.com, then the verification code would be sent by gmail to X@Y.Z, which in turn, due to your forward settings, would redirect all mail to A@gmail.com.
The difference is that when sending mail from your Gmail.com inbox as opposed to the Google apps inbox for X@Y.Z is that when you send a mail via gmail (even if you fake the sender), the signed-by field will contain "gmail.com". On the other hand, Google apps for domains will set the signed-by field value to "Y.Z" (which would be your domain name).
As far as I know, this is the only difference. In Gmail, you can even set the default sender-address as your custom domain address so you don't need to set it everytime you reply to/compose new emails. And, unless you think/feel that signed-by: domain.name is cool, you're not really missing anything.
It's pretty easy actually but when authorizing GMail to add a new sender address it usually mails a verification code to that address. Which, in this case would come back into the same Gmail inbox.
So if you have a X@Y.Z forwarding to A@gmail.com, then the verification code would be sent by gmail to X@Y.Z, which in turn, due to your forward settings, would redirect all mail to A@gmail.com.
The difference is that when sending mail from your Gmail.com inbox as opposed to the Google apps inbox for X@Y.Z is that when you send a mail via gmail (even if you fake the sender), the signed-by field will contain "gmail.com". On the other hand, Google apps for domains will set the signed-by field value to "Y.Z" (which would be your domain name).
As far as I know, this is the only difference. In Gmail, you can even set the default sender-address as your custom domain address so you don't need to set it everytime you reply to/compose new emails. And, unless you think/feel that signed-by: domain.name is cool, you're not really missing anything.