Both positions are awesome. Can't say one is better than the other as both feel really good if you enjoy bottoming. When the top cums inside you, being on your back allows you to watch his face as he unloads. This can add to the pleasure.
I like to stand up, legs wide apart, and bend over, resting my hands on my knees. An armchair is also useful. Once when I returned to the men's room after swimming, there was a man, probably in his late 50s, sitting in his wheelchair naked. I could see that he was aroused. I let him look at me for a while, in the nude as usual. Then I bent over facing away from him, legs wide apart, to get my clothes out of my locker, so that he could see my parted cheeks and dangling bollocks. I could see his reaction by looking at him from between my legs; so I positioned myself one leg over each arm of his wheelchair facing away from him to let him play with my arse hole and bollocks. Then I turned to face him. He did not need much help from me for him to come to orgasm. Then he returned the favour for me.
I looked through all these posts and realized my first one from 4 years ago still holds. But for deep thrusting, fire hydrant is great. For gentle grinding, me on belly with legs spread and his full torso pressed against my back, and he's breathing into my ear. And in a sling is nice, staring into his gooning eyes, whew.