Mike Evans does not equal Randy Moss. Bad comparison. Moss was the fastest player on the field and beat people deep. Evans wont be that kind of player.
Mike Evans by far - I think the gap between Watkins and Evans is pretty close and wouldn't be that surprised if he's taken first given he's much bigger but still a good athlete. I would probably take Cooks over Benjamin right now, but I'll have to see how Benjamin does at his pro day.
In my mind, there are 3 tiers of WR's which are pretty close to each other, but I know other people have different ideas (some may put Watkins as 1 and Evans as 1a or swap Benjamin and Moncrief):
1. Top 10 picks:
Sammy Watkins
Mike Evans
2. Mid first-early 2nd:
Marquise Lee
Odell Beckham Jr
Brandin Cooks
Jordan Matthews
Kelvin Benjamin
I think the 49ers may look at some of the tier 2 receivers if they are there at 30 and may trade up a little bit if they really like a player like Beckham or Cooks. The way these players are grouped, I think the difference between any 2 players in the group is smaller than the difference between the worst player in one tier and the best in the next tier (I'm not a big Marquise Lee fan).
Speed only doesn't mean much if DBs like in Seattle are going to be holding you and manhandling you at the line of scrimmage and beyond. You need a combination of size, speed, and physicality and coaching.
I like Cooks a lot, but it's not close. If Evans falls out of the top10, I think we're going after him. Evans matches up nicely with Seattle's physical style.