Moving to another horse?

Before I got Red, I had a miniature horse, Barbie. A lot of people think that the bond you grow with a mini is different than the bond between a horse and it's rider. I completely and utterly disagree. I had a wonderful bond with Barbie, I loved her to death. She taught me everything, she was my first horse, my problem child. We were told she was used for pony rides and she ended up being a wild little pony, crazy. We drove over an hour to get to this farm she was at and we found them herding her, roping her, just trying to get her to calm down before we got there. These people also had bigger horses and a couple other mini's. I think they were mainly horse traders. One of the ladies said they only had three horses that they would never sell, one being their younger daughter's horse. Then, I noticed the probably 13 year old girl, riding bareback and galloping through the pastures on her beautiful Paint, at first, I admit I was in awe of her riding. She rode very well, was confident, her horse and herself looked like a perfect match, then I noticed the rope. I figured, Oh, these people rodeo, I know that, she's probably just practicing!! Nope. She was roping Barbie. Barbie freaked. We couldn't get close enough to touch her, but we bought her and finally after just over a week she was delivered to our house since we didn't have a trailer. The people were a good three days late, no kidding, and we thought they'd never show!! For the next little while, we trained Barbie. In the end, she was an annoying, puppy type of horse. Followed you everywhere, was easy to catch, let kids on her back, jumped, stood for me to braid her mane and tail, she turned into a great horse. I loved her so much, however, later, I got the call about Red. Red needed a home desperately. I don't know if I've said this before, but Red was sold before I got him, then the people decided he wasn't show worthy and would take more work than he was worth. They thought he'd stay skinny and bald, literally. They had no hope for him physically. I *begged* my mother. Please, please, please let me take Red. I had proved myself with Barbie.I mean, I was out there several times a day, I did everything for her and I loved it. Finally, mom gave me a choice. Red or Barbie. Finally, I chose Red. If I'm going to be honest, my horse career would go no where if I had chosen Barbie, but that's not what I was worried about. Red needed me, and I needed him even more, however I didn't know that then. Barbie was about 31 inches, obviously the only people who would ride her would be my nephews and nieces, and also, she was pregnant. We've lost a mini mare from foaling before, we didn't have the resources to take her to a vet if needed. We ended up selling her to an amazing man with 29 other mini's and other big horses, turkeys, goats, dogs, you name it. She'd be spoiled by his wife, who had always wanted a miniature Paint like Barbie. He gave me my barrel saddle, too. :D Now, I ask you guys this question: What do you think about moving on to another horse as you either grow or become a better rider? Do you think you should stick with your older horse, or move on to a new one?