Beyond possible differences in manufacturers' equipments' reliability and quality (e.g., quality of balancing), fans and blowers are defined by their fan curves (cfm vs. pressure differential across the fan), and neither has a intrinsic claim to superiority that I'm aware of in any particular size range. They do differ in physical configuration; roof blowers are typically lower profile than roof fans. In-line units are usually axial fans, but large buildings may use large internal blowers in HVAC machinery rooms. (For visualizing the difference between a blower and a fan, see Ametek's website, or think hair blower vs. room fan.)

Repair of a unit on a high, steeply pitched roof difficult to access from inside an attic would certainly be harder than a unit on a wall that could be reached by a ladder. And it is also possible to install an in-line fan where it is hard to service, so every configuration has to be judged on its own merits.

Given adequate cfm at the predicted pressure loss, I personally would choose a configuration I could best access for repair or replacement. Visual appearance would be secondary, but that might vary with how obtrusive the best mounting location actually was.

kas

The only thing I would think about for an external unit is that I could see it, versus an inline that I could not see from the outside. Or inside for that matter.

Thank you both! External in this case would be easier to access, not that the inline would be horrible, but the inline also takes a long path.

I don't think it is that visible from the outside (it comes out 7 or 8") so one would generally have a side view from the yard if looking at the house or if you're walking in from the driveway through the gate into the back yard to get to the patio. If you are going straight to the back yard from the gate, you probably would turn left and not look at it. You definitely can't see it from the inside.

So, I guess external wins! Let's hope that they approve an exchange. Even so, the restocking fee is steep - 25%