Deriving Comparer(Of T)?

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VB

.NET

I was looking at IComparer(Of T)[^] when I found:
"We recommend that you derive from the Comparer(Of T) class instead of implementing the IComparer(Of T) interface, because the Comparer(Of T) class provides an explicit interface implementation of the IComparer.Compare method and the Default property that gets the default comparer for the object."

Something similar is recommended for IEqualityComparer(Of T)[^].

Now my question is: Why should I derive rather than Implement?
I do not find the MSDN articles clear enough at this point.
Maybe someone could enlighten me? :)

Edit:
I have currently implemented my IComparer like this:

Public Class OrderPriceComparer
    Implements IComparer(Of IOrder)

    Public Function Compare(ByVal x As IOrder, ByVal y As IOrder) As Integer Implements System.Collections.Generic.IComparer(Of IOrder).Compare
        Dim greater As Integer
        If x.CalculatePrice < y.CalculatePrice Then
            ' Y is greater.
            greater = -1
        ElseIf x.CalculatePrice = y.CalculatePrice Then
            ' Both are equal.
            greater = 0
        Else
            ' X is greater
            greater = 1
        End If

        Return greater
    End Function
End Class

It gets called like:

' Orders is a list of orders that needs to be sorted by price.
Me.Orders.Sort(New OrderPriceComparer)

For a default ordering of my orders I have my OrderClass which Implements IComparable(Of IOrder).
The implementation looks like this:

Public Function CompareTo(ByVal other As IOrder) As Integer Implements System.IComparable(Of IOrder).CompareTo
        Dim greater As Integer
        If other.ID > Me.ID Then
            ' Other is greater.
            greater = -1
        ElseIf other.ID = Me.ID Then
            ' This is just plain wrong, an ID is supposed to be unique!
            Throw New Exception("An order cannot be compared to itself.")
        Else
            ' This one is smaller
            greater = 1
        End If

        Return greater
    End Function

So I can now also call List(Of IOrder).Sort or pass it an optional IComparer to sort on anything different than ID.
Although I do have to make a new Class for every Property I want to sort on.

PS. I could not simply return the difference between x.CalculatePrice and y.CalculatePrice or Me.ID and other.ID because they are not Integers and I want to be safe for rounding differences and OutOfRangeException ;)