I'm trying to find out who had a lead score change from a specific smart campaign - would I use data value changed with a reason or some other filter?
The Data Value Changed filter with the Reason constraint is appropriate for finding leads that had their Lead Score changed by a campaign.
This screen shot shows an example of how you might set this up.
The list below show a few of the values you may see in the Reason field. If you know the exact phrase you are looking for, use the "is" operator. For example, "Changed by Smart Campaign Contact Us." If you don't know the exact value, try using the operator "starts with."
The Reason filter constraint is available in these filters: