I wanted to wait until I could get on my computer to respond to this topic as its a pain to type a long response on my phone.
I drive a class 6 truck and have put thought about moving up to a class 7 or 8 truck, but the more I research it, the more I will stay in a class 6.
The pros of staying under 26k are no CDL, or IFTA or apportioned plates, lower priced trucks and a different California emissions compliance table.
The cons are a little less weight capacity (more on that later), and trucks that will wear faster.
My current truck is a 2005 Hino 268, I only have a 24" sleeper (which sucks), a 24 foot box with a liftgate. My empty weight is about 15,500 so I can carry 10k legally.
The carrier I run for has one class 7 Hino that has a big sleeper, 20 foot box, no liftgate and it can haul 12k, so I ask the question, is crossing the 26k mark and the extra regulations worth the extra ton of capacity?
Now I have seen some nice class 8s out there also and if they are only single axle, 33.6k GVW, then the cargo capacity is back down closer to 10k because of the heavier duty components of the big truck.
In 2012 my carrier purchased 2 new freightliner trucks (under 26k) that had the integrated sleeper that is part of the cab, those trucks have 24 foot boxes and liftgates and were 80k new. When its time for me to get a new truck, I am going to go for another Hino 268 (hydraulic brakes), but going to go for about a 60" sleeper, 20 foot box and liftgate, im guessing that should be about 85k or so and should still be close to 10k capacity. I know that I am going to have to custom build that truck so going to be interesting.
The nice class 8s will last longer for sure, but since they cost 120k to 150k, how long will the extra wear and tear on a class 6 catch up to the massive extra cost of the class 8?
Unless you are going to haul lots of heavy freight, better in the longrun to go class 6, but that's just my opinion.