On the 100 it has the lock down piece to secure the spool. The pictures of the 50 I've seen do not. How does this effect the smoothness of the 50? No where local has a 50 but the 100's I've handles were amazing.

What do you mean by a "lock down piece"? I've never heard of anything like that on a Shimano low profile reel.

 

But my Core 50's do not have anything to lock down the spool, other than the spool tension knob.

Are you talking about the flipping reel?

The 100 has the red ring that you have to unscrew to to remove the spool after you remove the side plate.

The 50 has three tabs instead.  Since neither touch the spool, it has no bearing on smoothness.

Ok thanks.