76ers get: Seth Curry
Mavericks get: Josh Richardson, 2020 No. 36 pick (Tyler Bey)
Philadelphia 76ers: B

Daryl Morey's goal during his first offseason running the 76ers' basketball operations is clear: upgrade the team's shooting. After adding 40% career 3-point shooter Danny Green in a swap for Al Horford earlier Wednesday, Philadelphia has now acquired one of the NBA's best pure shooters: Curry's 44% career 3-point accuracy ranks second in NBA history among qualifying players, per Basketball-Reference.com.
Offensively, Curry looks like an ideal fit for the Sixers. With 6-foot-10 Ben Simmons and 6-foot-5 Shake Milton as its primary ball handlers, Philadelphia can afford to have the undersized Curry (6-foot-2) space the court in an off-ball role.
There's a trade-off at the defensive end of the court. The past couple of seasons, the 76ers prized collecting as much size and physical skills as possible, which caused the smaller Toronto Raptors problems during their seven-game series in the 2019 conference semifinals. By contrast, Curry's small stature for a shooting guard is why he has primarily been a reserve during his NBA career.
On the plus side, Philadelphia did need someone to match up with opposing point guards, who caused the team's bigger defenders problems at times last season. And Curry's on/off numbers on defense haven't been especially weak. Still, Richardson has generally been considered the better player of the two. So why were the Sixers willing to give up a second-round pick in this deal?
Aside from shooting, Curry's contract was probably especially appealing for Philadelphia. While Richardson can become an unrestricted free agent next summer if he declines an $11.6 million player option, Curry is signed up through 2022-23 at a reasonable average of $8.2 million per season. Both the long-term cost certainty and the slight savings from Richardson have value to a Sixers team in the luxury tax.
Dallas Mavericks: A

Although it was surely difficult to part with Curry, who's had two successful stints in Dallas, upgrading to Richardson makes a lot of sense for the Mavericks. With Luka Doncic and Kristaps Porzingis as cornerstones, Dallas has plenty of shooting and offense but could stand to upgrade defensively. After all, the Mavericks led the NBA in offensive rating last season yet finished 18th at the defensive end of the court.
Richardson should help. At 6-foot-6, he's big enough to defend any of the perimeter positions depending on matchups, giving coach Rick Carlisle plenty of flexibility as he deploys the team's other likely perimeter starters, Doncic and Tim Hardaway Jr. Offensively, Richardson is more than a zero. Dallas can reasonably hope for a bounce-back season beyond the arc from Richardson, a career 36% 3-point shooter who hit just 34% of his attempts last season.
Because of the Mavericks' cap situation, Richardson's player option isn't necessarily such a bad thing. If he opts out, that creates more flexibility for Dallas in pursuit of a max free agent next summer. Re-signing Richardson using Bird rights would remain an option if the Mavericks were to strike out in free agency.
Given all that, Dallas walking away from this swap with a pick in the early second round is nice work in terms of value.