It seems like maybe you have made up your mind, but here's my two cents.
Even though Twister is young and has great qualities the bottom line is (from what I understand in your posts) he's too much horse for you. If you prefer an older horse that you can feel comfortable on then I think that's the route you should go. Do I think this palomino is the right choice? I don't know, but I wanted to share with you how I came about Stella.
When I first came across her year ago, the photo in the ad was taken during the winter and she looked filled out in her winter coat. I requested a current photo and all they sent me was a head shot. When I went to see her in person I was appalled at how thin she was. Her hooves were also way past due for a trim and she was in this tiny dirt lot that wasn't large enough for one horse let alone the four that were kept in it. I had basically decided right then and there that I just plain wanted to get her away from those people even though I knew I was taking a huge risk. I got lucky, though, as it turned out she just needed some TLC. She has been so wonderful to work with. She's gentle, smart and so willing to please.
Now, I'm not saying I think you should do the trade, but at least go see the horse in person. You'll be able to put your hands on her, evaluate her surroundings and get a feel for what kind of people these are and if you'd feel comfortable with Twister in their care. Sorry for the book...