I agree with you. Play-off matches are very unpredictable. Sometimes some strong teams do not play with their main squad. There are even some seeded teams that get results that are beyond expectations. It is like the Lugano vs Besiktas match. Besiktas were highly favored in that match but beyond expectations the match ended in a draw after Besiktas won 3-1. Some strong teams that have won in the first leg did not play their first squad in the second leg because of the huge level difference. I think it is difficult to make a choice in play-off matches.