Morrow has the potential to be the best all-around WR out of this year's class, but there is no way at this point to know who will be the best WR. Also, Morrow may end up as a hybrid TE/WR or a true TE. He has the frame to carry a good bit of weight.
If I could have any WR in this class, I would want Brassell. I think he he has a better chance of making it the league by playing corner, but you rarely find guys with his explosiveness. He has the potential to get open deep on every play. Singleton has great speed, but I think he is somewhat overrated. In my opinion, Morrow and Moncrief are more likely to develop into true go-to WRs than Brassell or Singleton.