Technically, carbon steel tubing and mild steel tubing aren't different types of metal at all. Mild steel is carbon steel. (Technically, all steel is "carbon steel," since carbon is the difference between iron and steel.)
Carbon steel is alloyed with up to 2% carbon. What we refer to as "mild steel" has only 0.1% - 0.3% carbon. So, when we say "carbon steel," we're most likely referring to alloys with 0.3% - 2% carbon.
"Mild steel" is more of a slang term than anything else. Technically, it's more appropriate to reference "low carbon steel" vs. "high carbon steel." However, if you ask about mild steel tubing, your manufacturer should understand what you mean.
Advantages of Mild Steel Tubing
Cost - Mild steel is the least expensive of all types of steel. Although it's not as strong as other steels, it's perfectly fine for moderately stressful applications such as home & garden items. Its low cost makes it extremely competitive for these low-strength everyday applications.
Ductility - Mild steel tubing is easy to bend, and doesn't break as quickly as its harder sibling, carbon steel tubing. Higher amounts of carbon cause brittleness, leading to an alloy that is more likely to snap than bend. Mild steel's ductility makes it perfect for tube bending, shaping, and welding.
Environmentally Friendly - Like other steels, mild steel can be reused and recycled many times over.
Lightweight - Carbon is heavy. Mild steel's low carbon percentage makes it easier to handle than carbon steel tubing.
Disadvantages of Mild Steel Tubing
Mild steel tubing cannot be hardened by heat treatment. Heat treatments only affect carbon. If there's not enough carbon in a steel, there won't be any significant improvements.
Mild steel tubing isn't as strong as carbon steel tubing. Its ductility is also a disadvantage - mild steel cannot be used in highly stressful applications such as infrastructure or construction.
If your product is for low-stress applications and designed for consumer use, you might benefit from mild steel tubing's low cost and light weight qualities. We would not recommend mild steel for high-stress applications.