So the serial number is important, that's what I wasn't sure about.
Then in this case, both options are possible, if you create 300 products for each model, your customers will be able to search for a specific model easily but it will be a huge mess in your product listing (too much product).
So I would suggest to go for the variant solution. Note that you can create them by importing a csv or using the mass action system, it will make you gain a lot of time.
Also, if you use the variant solution, your customer will be able to select the serial number trough a dropdown so maybe you will want to hide out of order product which is an option of the main configuration (System>Configuration>Display).