Tylka,
I think our main criteria have been cost and print usage.  We have been
going to online only when there is a distinct price advantage--say 5-10%
savings.  We are also considering print usage.  If the print usage is high
we may continue getting that title in print as well as online, then
monitor usage in both formats to see whether print usage remains high.

Dianne Olson
Loyola Health Sciences Library
dolson@lumc.edu