When you stick something, like say a Vertex, into an XSICollection, you get a CollectionItem. But you can get back to the Vertex if you know how (via the SubComponent
).

si = Application
log = si.LogMessage
sisel = si.Selection
import win32com.client

oColl = win32com.client.Dispatch( "XSI.Collection" )
o = sisel(0)

print si.ClassName( o.ActivePrimitive.Geometry.Vertices(0) )
# Vertex

#oColl.Add( o.ActivePrimitive.Geometry.Vertices(0) )
oColl.AddItems( o.ActivePrimitive.Geometry.Vertices )
print si.ClassName( oColl(0) )
# CollectionItem

print si.ClassName( oColl(0).SubComponent.ComponentCollection(0) )
# Vertex

a = o.ActivePrimitive.Geometry.Vertices(0)
b = oColl(0).SubComponent.ComponentCollection(0)
print a.IsEqualTo(b)
# True
print b.IsEqualTo(a)
# True