I keep GMail apart from Outlook. That's partly because GMail is where I do stuff that I want to keep separate from work and personal email.
It is also easier for me to configure GMail as an IMAP service outside of Outlook.
That's really why I suggested that you start with what you want to do with the GMail stuff.
If you want to be able to find things across GMail and other accounts in Outlook, then doing it in Outlook might make life easier.
If you want to keep them apart, as I do, then IMAP might be the way to go.
Of course, even if you keep them apart there may be a way to create Confederated searches that bring Outlook and GMail together.
Your call really. I can't see much of a performance issue.
It is also easier for me to configure GMail as an IMAP service outside of Outlook.
That's really why I suggested that you start with what you want to do with the GMail stuff.
If you want to be able to find things across GMail and other accounts in Outlook, then doing it in Outlook might make life easier.
If you want to keep them apart, as I do, then IMAP might be the way to go.
Of course, even if you keep them apart there may be a way to create Confederated searches that bring Outlook and GMail together.
Your call really. I can't see much of a performance issue.