At those rates, financially it is a no brainer.
But, it will depend somewhat on just how sharp you are, and whether you can find an instructor who is experienced enough in multi training and not afraid of the aeroplane. Because with only 80 hours you will probably need a patient and confident instructor.
Even if it adds two or three hours to the usual minimum time to get a multi rating, it will be money better spent in the twin. There is little additional complexity, or speed, but you will need to be able fly more accurately than what would be required for the single. Like EXACTLY at blue line speed. On the upside, you will find a twin generally nicer to handle because the heavier they get the more that usually applies. Unless the design is a dog to start with, but Travelairs are sweet enough.