Toyhaulers are generally heavy. That being the case, you don't want a truck without the higher numerical gears. The Big Tow gears, in other words. So yes, if you find a truck you like and it doesn't have those gears, pass on it.
The difference? Non-Big Tow capacity is about 7200 lbs. towing vs the Big Tow capacity of over 9000 lbs. towing capacity. It's significant. You know you're going to tow and that what you're going to tow isn't going to be light, so you do not want a truck that didn't come with those gears. As mentioned, the gears can be added, but you haven't already bought the truck, so buy the right one for what you need it to do.