I always tell mine that the dog is my favourite.
I find DS way harder to get along with, he is incredibly intense, very bright, very creative, super difficult. He is exceptional (in my eyes), he is amazing. Some days I find him almost impossible but I love him. He is way more similar to me which creates some of the tension. He is also heading to teenage years and is awash with hormones which coupled with lockdown is not making for an easy situation.
DD is less "exceptional", less intense, still bright but way easier to be around and a much sunnier child. I love her, I love her cheerfulness and her positivity. I find her laziness and procrastination infuriating. Do I expect her positivity to last when she hits her teens? No.
So, currently I find one child easier than the other. They are both much nicer one-on-one so that might be the answer OP - try and spend time with them individually, they you don't find yourself comparing so much.
I'm also fortunate in that I have one of each so can have a favourite boy and a favourite girl, which makes life easier.