LRS and NDR cover overlapping power ranges and both run convection cooled with no fan to service. Asked which is better, the honest answer is that they are built for different cabinets.
What actually differs
LRS is an enclosed chassis supply: a perforated steel case that bolts to the panel or the cabinet floor. The LRS-350 series occupies 215 × 115 × 30 mm and the LRS-150 series 199 × 98 × 30 mm — long and flat, so they suit a panel with free wall area.
NDR clips onto 35 mm DIN rail alongside the breakers. The NDR-120 series is 40 × 125.2 × 100 mm: narrow across the rail, deeper front to back. It trades panel area for rail width.
How to decide
Choose LRS when you need the watts and the panel has the wall space for them, or when the supply is wired once and then left alone. Per watt and per unit volume the enclosed format is generally the more economical of the two.
Choose NDR when everything else in the cabinet is already on rail. Wiring stays in one plane with the breakers and terminals, and a failed unit can be unclipped and replaced without dismantling the panel — which is the whole argument when the machine is in production and the clock is running.
What does not differ
Both are convection cooled, so both need the clearance their datasheet asks for and both derate as cabinet temperature rises. Neither format is immune to being packed too tightly, and a DIN rail supply squeezed between two warm neighbours is derated the same way a chassis unit is.
Full parameters for every model in these series, including the derating behaviour and adjustment range, are on the individual product pages.