Shells: do I need an end weld?

[Flask]

I'm using shells. I'm on WF4. Should I define end welds or use Pro's Automatic Midsurface Connections?

I'm running an analysis on an assembly. Each component has shell pairs. I didn't define any end welds (there are a lot of surfaces) yet. When I look at analysis results, the stress contours indicate that parts are connected, but I still see a gap between them. Is there any advantage to using end welds over Pro's Automatic Midsurface Connections?

thanks!