other uses for inter-domain BGP data 
        

mapping topology data
aggregating IP to network prefixes
aggregating prefixes to origin AS
inferring contractual relations 
"bird's eye view" of the net - (AScore) 
predicting AS path taken by a packet

important question: can you get essentially the same information from either dataset?   (hint:  no)

indeed, even though often covering fewer ASes than a full BGP table,
skitter data shows bidirectional and transit connectivity
for a significantly more ASes than BGP data of the
best available quality and sampling. (totally non-obvious...)