The pic on your gelding, upper body looks great. I'd drop your stirrups a bit. That would allow you to get your leg back under you a bit more and allow you to push down your heels and have a good anchor. Imagine dropping a string with a weight from your shoulder, your shoulder, hip & heel should all be aligned.
The photo on your arab, I'd chock that one up to the saddle. You look much more comfortable in the first saddle on your gelding.
Life is like a camera. Focus on what's important, Capture the good times, Develop from the negatives and if things don't work out, Take another shot.