I picked up some Kadee 705 couplers for some HOn30 modeling and then started considering if they would be suitable for early rail use.
Personally I will stick with kadee 58s since for me, they operate nicely but are a smaller object than the #5. Link and pins would be the most accurate, but for HO scale that is too much of an added operating complication. O scalers like B Kempinski can use them accurately, but I prefer the additional scenery space HO provides for myself.
For my narrow gauge models these will be the go to choice now. They are much more reliable than the 714s and previous generation.
I use mostly the scale head Kadees on standard gauge cars, and usually the short shank whisker version. Some locos need a special shank shape and those get the larger head couplers. The 711 couplers look better, but they're a pain to construct and install. For HOn30, though, I use N Scale Micro-Trains couplers. Some of my small locos will need work to add those!
Modeling 1890s (because the voices in my head told me to)
I've used the 705s since the day they were released on my 1870s models. They were intended to be a direct replacement for the N scale micro-trains couplers in HOn3 and look much better. In fact I know one N scaler who is considering using the Kadee 705s on his models.