It's up to you. Don't forget it takes about 6 months to a year to really connect with a new horse so if you get a new one give him/her heaps on your time so you can bond, it benefit you both in shot and long term! Also consider if the horse you have been riding might hold you back? But at the same time you two could really excel because you have already established a connection... I honestly think it's up to you and your riding ambitions
If you enjoy riding at the level the horse you connect better wbuy him. If you want to compete more buy the other horse. I just had this problem myself, I had an amazing connection with a pony, but wanted to compete higher so I bought a horse that would take me farther. As we rode and worked together we began to connect, now we have a great connection. The more you work with them the better they get to know you and the more you connect with each other.
A horse who you have a connection with is a horse who you will be more dedicated to rather than one you may just view as a horse to ride. That connection will take you far, so if you want a horse for enjoyment that you can work with and progress with then I'd definitely buy the horse you already have a connection with.
However, if you're more of a competitor and enjoy competing and need a horse who knows his job, buy that one.