What is the difference between LDPE and LLDPE?

LDPE (low density polyethylene) has a highly branched molecular structure. That branching gives it good clarity, a soft hand feel, and forgiving processing on the line, but it tops out at a lower strength ceiling. LLDPE (linear low density polyethylene) has a more linear structure with short, controlled side chains, which packs the molecules more efficiently and produces noticeably higher tensile strength, puncture resistance, and dart impact strength.

In practice, this means LLDPE can often be run at a thinner gauge than LDPE while still meeting the same strength requirement, which is why a lot of down-gauging projects involve shifting some or all of a blend toward LLDPE. The tradeoff is that straight LLDPE can be slightly hazier and stiffer to the touch than LDPE, so a lot of structures blend the two to balance strength against clarity and softness.

Neither resin is universally "better." The right call depends on whether the application is driven more by strength and downgauging potential, or by optical and feel requirements.