Sampras had the better serve without doubt. The main reason for this is Roddick had a narrower range of variety and his American junior level thinking that pace alone would suffice. Playing against the top guys he was simply too predictable - 225km/h flat bombs served well within the service box don't trouble the top guys as much as variety and disguise. That's what makes a truly serve great and Sampras (as does Federer) had these things in spades.
Original Pro Staff 85, leaded to 370g, hybrid poly/syn gut set-up, 48-52-ish lbs.