Am I right in assuming going with this housing and crimping new terminals is easier/better than the cheap solder-on edge connectors? Or is that what everyone uses now?
Besides quality, the cons for the solder loop edge connectors is that if one pin breaks/worn out/etc then you have to replace the whole edge connector.
Otherwise, you have your usual crimping is more secure then solder and IIRC the crimped pins can carry more current then solder ones.
The only pros would be personal ones like they are cheaper, people don't know how or have the tools to properly crimp, etc.
Along a different path, if these pins are getting harder to find, what about replacement Jamma harnesses? i.e. In 20 years when I want, or need to rewire a cabinet I picked up, will that be possible?
It will always be possible, even if you can't find the correct type of edge connectors anywhere. What I would do in the absence of an edge connector, is solder short wires directly to each of the PCB's card edge pins, and attach standard Molex connectors to those wires (like a 24-position, as used in ATX power supplies; you'd need two of them to replace a 44-position card-edge connector for example). Then I'd attach matching Molex connectors to the cabinet's wiring harness.
Edge connectors in general will be around for a long time; for example, they are used in modern PCs for connecting video cards and such to the motherboard, but the type used in arcade machines (0.156" pitch and designed to terminate to wires instead of to PCBs) won't necessarily be around for a long time. Obviously Molex wasn't getting enough orders for their 0.156" pitch edge connectors to keep them alive; for how long will other manufacturers keep making them?