That's just their respective strengths: Van der Poel is more explosive, Van Aert is less likely to give up. But ultimately Van Aert's problem is that he lacks that extra gear in his biggest targets of the season, for whatever reason.
Yea. Van Aert is always strong, Van der Poel is just super strong on the right moments. Perhaps that makes Van Aert look weaker than he is on the big occassions.