Extra rows or Quantity Column DB Design Me and a coworker are seeming to disagree on this topic. 

The context is Product that have multiple components. Sometimes its multiple of the same component. 

I think its better to have a record for each component where as my coworker thinks its better to have a quantity column. Personally I think this is what a one to many relationship in db design represents in a very real since, where he is saying its easier to work with (he is more of a c# guy where I am the dba). So, I can def see where we might be coming at this form different angles.  

I guess since I am new to this, I figured I would ask the people who know better what their opinions are.

Which is better - extra rows per "product" or having a quantity column?
Your table structure is defined by the entity model it represents, not by opinions.  

If components need to be represented individually, e.g. if they have unique serial numbers, different prices, or arrive as separate shipments, this would warrant separate records for each. If components are indistinguishable from each other (cf. nails, bricks, or gallons of paint) there is no reason nor method to track each one separately.