I have an Audiophilleo 2, but have not used a u-Link. Actually mine has PurePower, which makes it outstanding. Very much worth my money.
How do you intend to use them/with what components?
Some complementary info: I don't use a coax cable between AP2 and DAC, which is convenient and saves me from spending on yet another audiophile cable.
Operation has been rock solid. It never had an issue, or any computer-like hickups so to speak.
Customer service has been excellent. Again, never needed nothing to be fixed, but I did go from Win XP to Win 7 to Win Server 2012 with Audiophile Optimizer and needed assistance with the drivers, and at times sorting out what was causing the lack of sound in a new configuration, and Philip always replied fast, to the point, and really helpful.
There was a converter shootout maybe from a couple of years ago put together by memeber Elberoth, I think, on computeraudiophile.com. I remember the AP was compared, but don't remember if the u-Link was compared. Maybe worth digging?
Hope this helps...some :-)