I consulted a friend, and we think we understand. Let me see if I do, by
reiterating your question:
When should a bit of functionality in an ASPX page be a user control versus
a custom control?
Now, if this is correct, we need to define "user control" and "custom
control" in this context, which I believe you mean UserControls
(System.Web.UI.UserControl) versus System.Web.UI.Control derivatives, right?
The most salient difference between these is the template itself, which
makes it difficult to share UserControls between different apps, as they
have to be loaded by their physical location (URL). So, at the very least,
you should use custom Server Controls when you want to re-use them in
multiple apps.
--
HTH,
Kevin Spencer
..Net Developer
Microsoft MVP
Neither a follower
nor a lender be.