Easy son and difficult daughter. How do you prevent favoritism when one kid is way more challenging than the other?

I am the father of 3 young kids. 5 year old boy/girl twins and an 18 month old as well. I am a stay at home dad and the twins are in kindergarten.My son is so much easier than my daughter. They have a late birthday (September) and we considered holding them back because we were worried about our daughter's maturity. We sent them and our son is thriving. Our daughter isn't as much. She is moving along but very slowly and doesn't have the same enthusiasm for school.She also has numerous sensory issues and a real defiant streak. She says no to everything and makes things so difficult. Trying to do her hair in the morning is ridiculous because she fights me the whole way. Getting ready for school is a struggle. She doesn't care about time outs. We have tried sticker charts and hoped that seeing her brother get rewarded would encourage her to behave. When that failed we tried having just a sticker chart for her. That failed worse. She is still throwing tantrums regularly. It's her way or the high way.As a result I find her twin brother so much more fun to be around. He plays with me without getting upset if I touch his structure. My daughter gets mad if I play the wrong way. We like to go outdoors and ride bikes and play some sports. My daughter hates being outdoors and throws tantrums if she gets messy. We had her evaluated for autism and she isn't autistic. She is just programmed on hard mode.How do I make sure she doesn't get lost in the shuffle. It's so much easier to want to spend time with my son. I spend an equal amount of time with the twins but have caught myself wishing I was playing with my son instead whenever my daughter has her meltdown. I hate that. I love my kids and don't want to feel that anymore. We have her in OT and it's improving but I'm worried that it will always kind of be this way. via /r/Parenting http://bit.ly/2CJ6bTO