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Actually they often don't have exactly the same output, because the no switchport suppresses some L2 stuff.
For a p2p, you often use the no switchport variant, but a couple of reasons why you might want to use the VLAN variant, you can use the SVI across a trunk port, allowing both a logical L3 p2p and L2. If you have a device that supports hardware redundancy, like a stack or dual sup chassis, if port supporting the p2p SVI fails, you can repatch to another port already previously configured to support the SVI. (In the latter, you wouldn't be actively using more than one port at any one time.)
