We then went into the real world with a Boston-based firm and compared moving PSTs to moving via imapsync.
One PST for a user took 15 minutes to export client-side. We did not even bother continuing to time after that.
Using imapsync (for email) and our mCalReader (calendars, tasks, contacts) we read that user AND TWO OTHERS and inserted all three in 8 minutes.
Or imapsync has at LEAST 6 times the throughput.
Our conclusion was that imapsync is MUCH faster. Our further conclusion is that for purposes of migration PSTs fall far short of ideal. PSTs really suck to tell you the truth.
In going through some of our previous posts, I discovered an interesting factoid that we published years ago when comparing client-side migration speed vs. server-side migration speed. Server-side was 2-3 time faster on insertion than a client side migration just for calendars.