Personally I would think that height may be a major factor depending on where you plan to travel. IE there are more bridges that are too low for a 13' truck on the back highways and byways. Some really great trials that you can easily go on are height limited, such as Yankee Boy Basin in Ouray Colorado. (You can google it and see what I mean.)
Then again one of the most common discussions on here is the need for storage and space inside the truck. No room for my shoes, or my cloths, or my self rescue gear etc.
If you feel like you have ample space in the vehicle as is, then you may want to really question your reasons to add more space. If you feel like you need a place that is a dinning area, and a different place that is a sleeping area you may want to really question how important the low clearance thing is for you.
So... Clear as mud? I guess the short answer is the same as every question on this forum when it comes to build ideas... IT is user preference, and no one can answer it for you mate.
Either way, love the truck!
"Do you know what a soldier is, young man? He's the chap who makes it possible for civilized folk to despise war." -Allan Massie