The "a" in the ranson note seems very distinctive. I don't know too many people who write it that way. One would think that someone central to the case who writes such a distinctive "a" would have to be presumed the author - unless someone was trying to frame that person.
Yes, Patsy's "hats" on her a's were distinctive to her - especially because she would go back and add them on sometimes.
On the other hand, the salutation "Mr. Ramsey" is written exactly the way John signs his last name.
I have no way to judge which is the most reliable of all the 1000s of handwriting analyses that have been done on that note. I just have to go with my own impressions to form my own opinion. Personally, I don't give the handwriting that much weight in the overall scheme of things.