I'd have to disagree with Geoff on this one - it's been a long time since I serviced one of those "good ones" (I assume the previous model of LSU in a carry-case) but I remember that the solder joints around the rotary switches and charger DIN socket regularly suffered with dry-joints (due to repeated disconnection of charger and switching on/off in service), charging indicator bulbs failed frequently (preventing proper charging), the stand-alone chargers usually went missing or ended up with the cases smashed and transformer O/C, all the soft plastics around the vacuum chamber tended to disintegrate over time plus vacuum seals and one-way valves were a bit of a pain to replace. The batteries were also Ni-Cd so they suffered with voltage-depression (oxidised plates, hence high-resistance internally, causing series volt-drops) and memory-effect (effective loss of capacity). Functional verification was also a bit messy - water and a stopwatch was required to test flow rates.
The newer model LSU is certainly easier for users to quickly check function, Technicians to verify performance and for either to change batteries as and when required (assuming operators also do the required checks). On balance I think the newer models are more reliable but when they fail they're likely to be more expensive to repair unless it's simply problem related to a faulty battery. The newer models are mechanically more robust, in my opinion, and have preset vacuum adjustments (the older models of LSU required an optional, external, regulator valve/gauge). The inclusion of an in-line filter should prevent expensive replacement of the internal components (otherwise they will eventually seize-up after a period of being contaminated with "aerosol" from aspirated fluids in the suction container). Use of disposable liners is preferable and cost-effective since they usually have a filter incorporated to protect the suction device - if there is internal contamination then replacement of the mechanism means the device is a write-off.