Some really good additions and nuances in the comments. I think it is safe to say that both systems can actually work for a wide overlap of applications. It's probably at the extreme ends of usage (e.g., road race vs. city commuting/errand running) where either system starts to shine on its own. For the leisure/fitness/cafe road riders, it's more of a slight preference and priority decision. It's good to have that choice to suit our needs, there is no 'better overall' and the differences are arguably a bit smaller than a newcomer may expect based on reading up on differences for the sake of pointing out differences. As someone who rides near daily with no set destination, hills on the weekend, and the odd gran frondo, I simply should not have gone SPD based on unfounded concerns, that is all.
That said, it is clear that shoes seem very important, regardless of the system, but perhaps a little bit more with SPD given the smaller cleat. I think it's a good idea to spend as much as feasible on foot comfort and sole stiffness, it is simply too crucial of a contact point to cheap out on that interface. I had Shimano XC501s for SPD and switched to Bontrager XXX for SPD-SL, both with arch support insoles and bike fitted cleat positions. Both shoes worked great in that the pedal interface when riding was never top of mind, which is always a good sign. Things you overly notice are often in need of further tuning. The XXX is the better shoe due to the full carbon sole at double the stiffness and bi-directional BOAs which are a great upgrade that allows for easier mid-ride adjustments without popping out the BOA - better be for over twice the price. I do appreciate the new setup when working hard up hills or really putting power down, it is a matter of those slight differences falling into place to make the pedal interface ever so slightly more suitable to my riding. I could totally see myself having both systems, as some here have, if I had more bikes to cater for different riding scenarios.