I get what you're saying but your argument is based on maybe 1 college player every few years (Charlie Ward, Antonio Gates, Tony Gonzalez, LeBron, Allen Iverson, etc.) that could be a top prospect in both sports and the rather recent contract situation of the NBA.
In that rare case yes you'd be dumb to take the NFL over the NBA for the reasons you listed. It's based on the NBA's contract rules, not that the contracts are commensurate with athleticism or talent as you suggest. Your argument doesn't illustrate that NBA players are more athletic and talented than the NFL though.
> I don't believe any NFL player would score higher than Russell Westbrook or LeBron James in the Olympic decathlon.
Well I disagree and we can look at history for more evidence:
- Milt Campbell won gold in the Olympics decathalon [1]
- Jim Thorpe won the decathalon and pentathalon. Considered one of the greatest athletes ever. [1]
- Darrell Green ran a 4.43 forty at the age of 50 [2]. His best was 4.15 and he had an official 10.08 100m. "Darrell Green was so fast that when they had a competition in different events (baserunning, track, 40 yd dash) Green wiped the floor with rivals, including nine time Olympic medalist Carl Lewis.... while Green never beat him in track competitions (they ran against each other in college), Lewis points out that Green was a world class sprinter, and again really fast." [3]
- Glenn Davis won Olympic titles in the 400 meter hurdles twice. Davis was either at or close to world records in many events including: 100 yards/meters (9.6/10.3), 200 meters (21.0), the half mile (1:52), 120 yard high hurdles (14.0), 200 meter low hurdles on curve (22.5 WR), 400 meter intermediate hurdles (49.2 WR), high jump (6-8), and long jump (24'8"). [4]
Kind of fun looking some of this stuff up. I learned that Carl Lewis was drafted by both the NBA and the NFL even though he never played in either sport. [5]
The NFL has a variety of Olympic wins including: decathalon, pentathalon, freestyle skiing, bobsled, hurdles, various sprint, shot put, long jump. [1]
The NBA's history in the Olympics is nearly non-existant. The only one I could find was Marion Jones (1 yr WNBA) and Carl Lewis (NFL & NBA as noted above but didn't play a game in either).
[1] http://www.nfl.com/photoessays/09000d5d82aed82d
[2] http://bleacherreport.com/articles/346647-darrell-green-50-y...
[3] https://dc.sbnation.com/2010/9/17/1694402/darrell-green-wash...
[4] https://en.wikipedia.org/wiki/Glenn_Davis_(athlete)
[5] https://en.wikipedia.org/wiki/Carl_Lewis