Hello Marcel
I understand the dilemma. For SW2, both scenarios will cause a less-than-optimal load-balancing scenario. By default, the source MAC address is used, so even if you don’t configure any load balancing, it will use the source MAC to load balance. One thing to note here is that load balancing configured on a particular switch for port channels always affects the outgoing traffic.
The solution to this particular scenario would be to base load balancing on both the source and the destination MAC or IP address. That way SW2 will more evenly distribute traffic across the port channel.
I hope this has been helpful!
Laz