Wether you use an aftermarket or a stock replacement harness really depends on what you want out of the car. If you are going full mod, if you are restoring or if you are just looking for a lower cost alternative to the more expensive factory style harnesses. If you are going solely from a price point, the aftermarket offerings look attractive. The downside is the extra time you are going to spend in actually doing the wiring. Painless has sold a lot of harness kits, Francis will actually tailor a kit to your needs and requests, (so I've heard from the A body site), and American Autowire has some really good offerings with well thought out components and some of my favorite fuse panels. I use Autowire kits in most every custom I do now. None of these kits are Mopar specific. My experience is that Painless and Francis come from Ford backgrounds and that Autowire is GM based. (As far as design, wiring coding, whatever, goes). Nothing wrong with that. All of these kits will require making the connections for your end items like, lights switches, relays, starters and so forth, including gauges. Not hard, but not plug and play.
If you're looking for rewiring your stock/mostly stock vehicle, save your dimes and your time and get a stock replacement harness. It will bring your electrical system back to as new condition with little effort and be easier to troubleshoot down the road should you have to.
