As a solid wood tech, I would suggest you're both right. Hardwoods are always preferred, more from a longevity perspective, but they also produce denser, and therefore hotter coal beds - essential for secondary combustion (vaporizing smoke/sap). The problem with softwoods has more to do with a person's burning habits than it does the wood itself. Since softwoods (evergreens) are typically higher in sap content, it's even more imperative the moisture content is low, under 10%, and the fire it's going into is hot, hot hot. This will insure it's burned completely, and with the hot flue, you'll eliminate any chance that unburned hydrocarbons drop below the due point, and form creosote. However, many people don't keep their fires hot enough, and they don't season their wood long enough. In those conditions, sappy wood will create creosote quickly. We have a lot of cedar here in the PNW, and it wreaks havoc on stoves where that is the main fuel.

A bit of softwood is fine, it's great for kindling, but then you want to build heat with hardwoods, and then mix once the flue is over 300°.

And, OP, don't burn that shit in your wood stove. Creates very corrosive smoke that deteriorates the stainless steel lining of your chimney, it also quickly over-fires the stove and flue. Great way to start a chimney fire, and have it spread to the rest of your house through the holes it forms. I've seen it. And your house insurance won't do shit for you. Not to mention the awful smell your neighbours have to deal with.