When to combine facts from different systems...

Hello, I'm having a heck of a time wrapping my head around some of these concepts, neither way that I'll think of seems better or worse
to me:

We're a physical & electronic newsletter publisher. We have 2 systems, the physical system stores subscriptions when they start/end money paid etc.
In the case of print newsletters, the start/end is determined by issues remaining.

We also offer free ezines, these subscriptions have start dates, but no end dates, no issues no money paid.

I've modeled the "product" dimension to contain both types of product pretty easily, it makes sense in my head. However, some of the FACT tables are muddier to me.

For example, one of the facts is "issue sent" (a physical in the mail issue), which issue number, to who & when etc.

There is a similar fact in the email side, 'email sent' for the free ezines.

I can think of a way to combine them both into 'issue sent' but should I?

Should I treat those as separate facts? I'm unclear as to the pros/cons.

Any thoughts appreciated, I can provide more details if this is too unclear.

Thanks!

Just a guess, but I would assume the dimensionality is different between the two. I would probably go with separate facts at the atomic level. You can always build an aggregate that combines the two at some level to make general reporting simpler.