Do any of you know if there is a difference between the performance of these? Specifically, is there any extra signal loss on the feed-though type?

A feed through is just like using a coupler. There will always be added resistance to the connection when reconnecting. The best approach is to reduce the amount of resitance by having the least amount of distance between the jack and the point of entry the catX makes (cat5/Cat6). Cat5 and Cat6 also have different "rules and regulations" for what maintains the signal quality.

For all of the installs I have been involved in (both cat6 and cat5), punch downs have been always preferred over pass-through.

Make sense?

That makes sense- thanks.