They are essentially the same. Omnipotence is more in control and powerful but Reality Dreaming is Reality Warping but is powered by your most inner dreams and wishes, meaning there are little mistakes involved in its use.
As a human i would pick RD, its much more user friendly. In fiction i would almost certainly pick OP.
In a way, reality dreaming is the fun part of Omnipotence, no god complex, no evil speech about world domination or destruction, and no world peace to maintain; however the fact is that dreaming is mostly about random things (and no, I'm not including lucid dreamers, and especially not WILD ones), so in a way there is kind of disappointement.
On the other hand, Omnipotence is about perfect self control (PR Beyonder is Ultipotent, but he's a perfect exemple of how you really need to be beyond everything in order to not go crazy with that), so you are above everything, but you can't really do that much with said power IMO.
^ You're implying Omnipotence comes with a god complex, an evil speech about world domination/destruction, and world peace to maintain when it doesn't have to. Beyonder went all..well...Beyonder because he retained a personality that allowed for a dissonance with reality. The lack of knowledge is what sets Omnipotence and Ultipotence apart and ultimately decides what kind of personality you have if any (which is why some people prefer Omnipotence variants that clearly allow for the user to retain their original personality). Look at TOAA. He doesn't seem to have a problem with his position/power. In fact most of the users listed don't seem to have problems that we associate them with having (i.e. boredom). Why? Because they're Omnipotent. We can only go so far with understanding how an OP being would work that I think I'd settle for Reality Dreaming - nice and simple. We can understand easily how it works + a user like minus allows us to see what's possible. Keep in mind that when I talk about OP, I'm referring to the whole package (Omniscience and all - which I think is mostly why personality can change if a being somehow received OP).