If you fly F then SEN does not get you much other than one extra piece of luggage (4 instead of 3).
For me the best perks of SEN is much better award availability (like F on Swiss) and the companion award (2nd person pays only 50 % of the miles).
Otherwise you have some extra luggage, a different hotline phone number with less waiting.
The benefits are more valuable when you fly economy and you have lounge access and priority check in etc.
Others will have better answers than me.