There is no denying that in his prime Dez Bryant was a far more explosive and effective player than Dwayne Bowe, but when attempting to find a wide receiver whose career is most similar to Dez Byant's, for the purpose of a regression model, Dwane Bowe is the most apt comparison.
As for similarities: Dwayne Bowe was listed at 6'2 221, and Dez Bryant at 6'2 220. Dwayne Bowe was the 23rd pick of the 2007 draft and lasted 8 seasons with his original team Kansas City before spending a last season in Cleveland. Bryant meanwhile, was the 24th pick of 2010 draft and has just been released after his 8th season with his original team in Dallas. Dwayne Bowe retired after 9 seasons with 537 receptions 7208 yards and 44 touchdowns, his last season in Cleveland a non factor (5 catches 53 yards), while Dez Bryant is currently sitting at 531 catches 7459 yards and 73 touchdowns. Furthermore, both enjoyed 3 1000+ yard seasons:Dwayne Bowe at age 24, 26 and 27; Dez Bryant at 24, 25, and 26. Bowe only reached double digit touchdowns once in his career, fifteen in 2010 his age 26 season, but Bryant reached the mark thrice, taking place in his 2012-2014, age 24-26, seasons mentioned above. They may be more athletically similar than one would think as well, as Dwayne Bowe ran a 4.51 40 and had a 33 inch vertical at the 2007 NFL combine compared to Bryant's reported 4.52 and 38 inch jump at his pro day for Oklahoma State in 2010.
In term of on the field product both players are similar as well. Both play a brand of football predicated on strength, jump ball ability, and run after the catch skills. During their primes, Bowe and Bryant were both number one receivers who dominated their opposition physically playing with a "bully" attitude. They were routinely able to wrestle away highly contested balls and make circus catch look easy. They were both excellent at high pointing the ball, but Bowe (through lack of viable QB) never developed the back shoulder throw/route combo that Bryant and Romo did. Not only did they bully defenders, but at the earlier stages of their careers they both featured a sneaky athleticism and ability to take the ball to the house from any distance. Both were able to run through weak tacklers while cutting on bad angles in the secondary to create big plays for their respective offenses. Bryant was more explosive and elusive (Bowe was never utilized as a punt returner as Bryant was for a reason) but it was a similar style of open field running. For both of them, the slant was a go to route as it took advantage of both their size and strength in boxing out the corner, but also their run after the catch ability to generate yards in the second and third levels. Neither would be described as even a "good" route runner, as they won primarily on physical ability and less on nuanced skill and footwork, working almost exclusively from the outside with routes like go's, posts, and curls.
Both players have declined similarly as well. Statistically after age 27 both have hovered around 60 catches and 650-800 yards fairly consistently with the touchdown discrepancy favoring Dez even more in this stage of his career as Bowe (and the chiefs offense as a whole) really struggled to score. It is worth mentioning that both players were force fed as regressing top receivers in offenses lacking aerial options, neither were pushed to the outskirts by younger emerging talent as a reason for their statistical decline. Both players seemed to be sapped of speed at a rate more rapid than that of other players and both lost their ability to separate first. The speed is a killer because it really hampers and negates their skills as a ballcarrier. You'd think they'd still be able to outmuscle opponents for 50/50 balls, but that is an inconsistent and dangerous throw as those throws are tight window precision throws not all quarterbacks are capable of making, especially with consistency. They were able to win on throws with little separation before, but no separation is different and the quarterback will always be reluctant to throw the ball to a receiver who is consistently smothered, and safety help over the top becomes all but assured. The 50/50 balls then go from organic plays to designated play calls like fades where coaches are sure of the one on one matchup they're engineering, and when those play calls fail and the receiver goes through a dry spell on jump balls then he appears completely useless. When you combine that skillset with a poor locker room reputation then it begins to make sense why Bryant is still unemployed this late in May.
Bryant entered the league a year younger than Bowe, and has been a better player (3 pro bowls 1 all pro bowl to Bowe's 1 pro bowl) so its fair to assume he won't regress quite as rapidly. That said, it seems that a continued regression is in store for Bryant unless he makes some kind of drastic offseason training changes. Larry Fitzgerald suffered a similar physical decline but had developed his footwork, quickness in and out of breaks, and route running enough to build a second career as a slot receiver. Bowe was obviously unable to evolve his game. Fitzgerald was always a technician though, and expecting Bryant to learn a new route running repertoire in one offseason is an incredibly tall and unlikely task.
I expect Dez Bryant to sign with a receiver needy team sometime in June/July after injuries start taking effect. As a featured option he should be good for another year around 850 yards and 8 touchdowns, but carries the potential for a disaster season like Brandon Marshall recently with the Giants, or Dwayne Bowe in Cleveland. It wouldn't be surprising if Bryant is retired by the 2019/2020 seasons.