Let's compare.
Vassell is a vastly superior player to Whitmore, but Cam is in the second year of a 4/16 deal whereas Vassell is in the first year of a 5/135. Kings are currently hard capped at the first apron, and may value getting more cap flexibility with the "promising young player". However, Advantage Spurs.
Reed is a vastly superior prospect to Tre Jones. Tre is an expiring, and even if he were useful to SAC this season, he wouldn't be there next year. He's just an expiring salary filler. Advantage Rockets.
Adams and Green are just expiring salary filler. No need to think about them as anything else. No advantage to either team here.
Picks:
Spurs best picks to offer are best of ATL/SA 25, 26, 27. After that, I'd say best of DAL/MIN/SA 2030 and then Best of SA/SAC 31 and MIN 31.
Rockets have PHX 27 Unprotected which is pretty juicy, best of HOU/BKN 27, and Best of DAL/PHX 29. If they put those three on the table, accounting for natural variance I'd say those are just about as good as SA's. Where we have the advantage is we can offer the better pick in 25 and 26 if a quicker pick were a priority to SAC.
If it comes down to Vassell + filler versus Cam/Reed + filler, and the picks are a wash, it will depend on whether or not SAC wants Devin's long term salary. It also depends on whether SAC views this as a rebuild or a retool. If they are rebuilding completely, they won't want Devin's salary and age versus Reed/Cam. If they are retooling, it more than likely favors the Spurs.
The two teams competing offers are closers than most Spurs fans would want to admit, IMO.