In my humble opinion the Bennett system is more reliable and easier to service, especially for a vessel that stays in the water. The Bennett actuator has only 1 moving part, the ram, and the seal is on the piston, not at the bottom of the actuator so growth does not impact seals. Most problems that one may encounter with a Bennett system will be electrical in nature, switch or pump related, and repairable inside the boat. I've cut the chicken poo pump connector off and replaced with real connectors for instance, because I kept having to mess with the damn thing.
Lenco systems are simpler in that they have fewer components, but their electric actuators are underwater and would probably require a haul to replace if they were to fail.
I have personally had Bennett Systems that came on a used boat (see my avatar) that were a decade old, and still work a decade later. I did replace the switches.
I have never owned a Lenco system, and electric component below the waterline on a trailer boat might be fine, but on a boat that stays in the water...