Generally...
Bibs
Pro's - No butt crack to show, No tight waistband, More comfortable
Con's - usually more expensive, possibly harder to get a good fit (if u are excessively heavy or small for your height), hard/akward to go to bathroom in
Shorts
Pro's - Easy to go to the bathroom in, cheaper
Cons - Tight waistband, Butt crack can hang out, less comfortable then bibs
go with bibs