Rafter was clearly better. He was underrated at the begin of the career, Becker called him a jouneyman, but he made the most of his abilities, by hard work and athletic regimen, and a simple, but strict match plan, to come to the net and crowd the net all the time. He was in the eyes of many the best player of 1998, including the people of Tennis Magazine, who included Davis Cup results and named him player of the year. Without the injury-stop late in the season, he might have ended as formal ATP Nr. 1 on points. Was utterly dominant on American hardcourt that year, and had a 2-0 lead over Sampras, who played good, maybe not the best tennis. His kick serve worked well on hardcourt, it kicked so high, that all had problems to keep the return in play. The kicker wasn't as effective on grass, it stayed too low, and so incoming Rafter had to volley more from his toes. His volley was good, especially his forehand volley, albeit imo not in the class of the volley of prime Pat Cash, who hit cleaner volleys from a straight back.
Henman had a textbook style, maybe too textbook. He lacked the overall Whumms, the dangerous weapon and the real penetration of his shots, although the Brits always seeded him pleasantly at Wimbledon. In that department, he was like other textbook players like Charlie Pasarell, Woitek Fibak, who had an even more fluid allround game, or Jacub Hlasek.