I would say that during ASoS, both RW's were pretty heavily involved in helping the band to find its direction and there wasn't really a clear single leader. David Gilmour hadn't really developed his style independent of Syd Barrett (whom I believe he'd been instructed to emulate), in any regard. That came later. If you look at the credits of Saucerful and also take note of who sings what, the idea that it was probably both RW's pulling the weight pretty equally seems plausible. Roger Waters would eventually develop a direction and clearer style in lyrics (which was still in an early stage on ASoS). Richard Wright's style, both in keyboards and vocals, was already recognizeable and probably helped very much in easing the transition by giving fans something consistent to hang onto. And accordingly, he's pretty prominent on ASoS. Of course, I wasn't there and I can't know for sure, but I think this may be what happened.

Over time after ASoS, the RW-DG combo got more overt power (though for awhile Mr. Wright was still very influential in a more behind-the-scenes capacity), until finally it was just Mr. Waters, and then the whole dynamic shifted again with his departure.

I hope that answers your question pretty throughly!

By the way, I leave you with some food for thought, slightly paraphrased: "A choice not to lead is not the same as choosing to be a servant."

__________________
"And with these words I can see
Clear through the clouds that covered me
Just give it time then speak my name
Now we can hear ourselves again..."

WrightSatellite #1