Having been a step mom to pretty descent kids and having been a member off and on for 11 years I feel confident saying I think step dad's have it easier. 

Forr those who don't know my story I had a husband problem not a skid or bm issue I discovered after 8 yrs of marriage and divorced so I am a remarried bm only now.

My newer  husband ( who some days drives me nuts) had 3 step dad's as a kid and young man. Two bad one good. He has no kids and has a pretty great relationship with BS11.

Today he totally stole my son on our weekend. They planned a guys afternoon of bowling and sport collection shopping leaving me solo. I joke about the stealing... I am thankful they are buddies.

In our home my husband is tthe adult and gets to act as a parent with rules ect.... I feel that makes the difference . I think when parents don't allow their spouses adult status and let kids rule it ruins the relationships.  I am the ultimate decision maker regarding bs  in our home but it is wrong to expect your spouse to have no input. In our case it works because my husband treats him like his son w/out diminishing my ex.

Works out for me too because I don't have to go sports collectible shopping:).