PD engine cams, by design, will always be a weak spot. That said, it doesn't mean they cannot last a reasonably long time with proper care. My BHW has 210k miles on it, valve cover has never been off, likely never will be.
All three of the PD 4 cyl engines sold here, BEW, BHW, and BRM, have various differences between them, including the camshaft. While they are all the same basic engine family, they do not share many parts.
Key differences:
BEW and BRM are 100hp 1.9L, BHW is 136hp 2.0L
BEW and BHW have a CKP sensor in the block, with a tone wheel on the crank. BRMs have their CKP sensor in the rear seal flange, and the tone wheel is integrated with the seal itself. CMP sensor is different too.
BEW and BHW have the water pump o-ring fitted to slide INTO the block with the pump body, BRMs have the seal on the front surface of the block.
BHW and BRMs have open intake ports, single runner. BEWs have a split intake port with dual runner control flaps.
BHW has a Valeo "log" style EGR cooler, with no bypass flap. BRM has a Valeo log style cooler too, but with an intagral bypass flap that ALWAYS eventually leaks. BEW has a Modine "waffle" style EGR cooler, with a separate bypass flap assembly.
BEW and BHW have a vacuum reservoir remotely mounted on the engine (BEW up front, below the glow plugs, BHW down low, above the A/C compressor). BRM's reservoir is integral with the valve cover.
BHW has an EGT sensor, the others do not.
BEW and BRM have a VNT vane sensor, BHW does not.
BEW and BRMs use Borg Warner turbos, BHW has a Garrett.
BHW has a chain driven dual balance shaft module, which needs to be upgraded to a gear driven version or it will blow up (you can also "delete" it, but in stock form it will vibrate more).
BEW and BHW are subjected to the "glow plug fiasco", which meant software and plug changes from the factory. BRM never had this issue.
BHW is mounted longitudinally in the car (B5 Passat), BEW and BRM are transverse (A4 G/J/NB, A5 Jetta, respectively).
BHW uses two accessory belts, one for the A/C compressor, another for everything else. The others only have one.
Much of the differences are a result of the orientation in the car in which they are installed, like the shape of the oil pan, and not necessarily differences in the engine proper. But I outlined the main differences.