Definitely not. The posts me, Ethy, and Chaser have posted for both possibilities are comprised entirely of facts about why either will be in the Realm of Sleep and how they will contribute. While both can be in it, Data Riku actually has a purpose to serve and help exploit in order to help Sora and Riku understand the situation about the people they have to save since mickey's letter was useless, while we don't know what Repliku can help accomplish in the storyline in the Realm of Sleep, if he should be rescued, and whether he's even going to be on the same side as both Sora and Riku in the Realm of Sleep.
Data's explanation has more facts to back up it's purpose while Replica only has a reason and not a purpose to sum up. Man, this is just a big cycle. People ask questions, we answer them, they side by the losing team on opinion terms, and then ask the same question again. Amazing, is it not?