Ours will give you the "direct" route. Not the fastest route. So usually even if it is faster to go 4 miles over to I-## it will keep you going back roads through small towns. Though this morning buddy of mine said it was going 23 miles farther on his route in CA on 99. Hammer was giving 100 miles. "Jill" was giving 123 miles. Again off of 99 and onto side roads. I've not once used it since I got in my own truck. It is POS.
I'd check the route setting preferences on those units. Sounds like they might be set to exclude certain types of roads etc... I finally figured that out after wondering WTF their routing was coming from.
Qualcomm do have some quirks. My company used to use Qualcomm. I noticed once it always gave me weird routing if I had to go into Spokane. I finally figured it out. While most of our vans are the usual 13' 6" variety, a few are of the 14' height. The Qualcomm would route automatically for a 14' height clearance. It just so happens there's a railroad underpass with only 13' 8" clearance, which was the easy route in and out. But, the Qualcomm wouldn't use that route because of the height issue, although a regular 13' 6" trailer would fit just fine. 9nce I figured that out, I naturally went the easier route in and out. Always went kinda slow through that underpass, but always fit just fine.
In the end, I've come to the strong opinion that too many drivers rely way too much on their routing devices. As a professional driver, it is 100% my responsibility to route myself to where I need to go. So, I always evaluate the route these devices give to ensure it makes sense and is both safe and legal. As a former cartographer I do have a bit of an edge in that department. And, I understand the different methods they use to weigh routes and create them. But, they are far from perfect, even the best of them. But, regardless, blindly following any routing device is folly.