I base my observation that soccer requires greater athleticism than baseball on my own experience and just watching the pros do it. After sitting on my couch all month which sport is going to be easiest for me to go out and play this afternoon? I could get through a baseball game pretty easily. I might not catch or hit that well, but those are skill issues. Just like my passes and shots in soccer would be off. But I have a seriously difficult time getting through a soccer match if I haven't been exercising recently. Just being able to run for such a long period of time and still be able to sprint when the occasion arises.It's not an issue of one sport being better than the other. Compare baseball to football. There is one big reason why you can only play one football game a week, but you can play several baseball games in a week. It doesn't mean that football is better than baseball. And soccer requiring greater athleticism doesn't make it better than baseball.
I take a look at soccer players at the end of a match and compare them to baseball players at the end of a game, it seems to correlate with my own personal experience.
Hypothetical athlete substitutions don't tell you anything. This isn't "Shaq Vs." These guys don't have the skill sets to play each others' sport. Just make them run laps until the first one passes out.