Comparing basic strength of acetamidine and 2-imidazoline

[![Structures of acetamidine and imidazoline](https://i.stack.imgur.com/2fJG7.png)](https://i.stack.imgur.com/2fJG7.png)


My approach:


1. Conjugate acids of both molecules have the same number of stable resonance structures. So no conclusion from here.
2. Conjugate acid of 2-imidazoline will have negative inductive on the lone pair donating nitrogen by the other nitrogen atom. Since this effect is absent in acetamidine, acetamidine should be a stronger base.


Is the above approach right? Can ring strain affect the basic strength of 2-imidazoline in any way? Should I consider any other factor too to make the right comparison of the basic strength of the above two molecules? 


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