Bear in mind that, with one exception, I use a delay pedal just for slapback. In 2012 I bought the green box Joyo analogue, because it was cheap, and the internet told me that analogue was best. I have been very happy with it, and it has worked faultlessly, £23 well spent. In the search for a simple board in a single pedal, about six years ago, £44 bought me a Donner Alpha Cruncher. This is ok for slapback, but excels for the intro to kool and the gang's Celebration. A bit longer delay and brighter, more in your face. Having decided to put together a mini board and reading loads of great reviews spent another £23 on the yellow fall. The mini board never completed, but it occasionally replaces the Joyo when I juggle the board. I sounds great.
I'm happy, maybe just lucky, maybe everything does slapback well, maybe I don't know what I'm talking about, or have never experienced something exceptional, or would recognise it if it hit me in the face. None of these cost a great deal of cash, in total I have spent about half the cost of a memory man or carbon copy. For what I need I'm happy.