Both pants get sold as 'work pants.' They're not the same tool.
Rothco BDU. Military-pattern battle dress uniform pant. Six pockets, including two large cargo pockets. Cotton-poly ripstop weave. Lightweight, fast-drying, built to take abuse but not specifically designed for kneeling. Costs $40-55. The unsung favorite of utility, security, EMS, landscapers, and anyone who needs to carry stuff in pockets.
Carhartt double-front. Heavyweight 12 oz duck canvas with a second layer reinforcing the knees and shins. No cargo pockets. Designed for kneeling work — flooring, framing, masonry, anything where the knees are on the ground. Costs $70-90.
When to pick BDU. You're carrying notebooks, gloves, a multi-tool, a flashlight, and you need to keep both hands free. Your knees aren't on the ground much.
When to pick the double-front. You spend hours kneeling. Knees on subfloor, on concrete, on tile. The reinforced layer is the entire point — it's where the pant fails first on standard work pants and the double-front extends life by 2x or more.
Bonus. The double-front has a knee-pad pocket on most cuts — slip in a knee pad and you're set. We stock both Rothco and Carhartt. Different walls, different shoppers.