Well this will come down to you get what you pay for, if it meets your expectations and functions as expected, plus you are happy then great but as you have found the calibration is not so easy as it would be on the Woodpeckers version. These parallel guides need to be precise in order to be useful, both will need to be exact if you are to get a parallel cut and it may just be that they require more time in setting up. If you dig into Peter Millards video's there is one where he made some parallel guides using Ply and so I would have thought your cheap ones would be at least as good as those. I recently brought some items from the slow boat from China and they are not in the same league as Woodpecker, Jessem and such but for my intended use they will be ok because I am not looking for precision but repetition. Mikes link to the video shows how Denis sets his ones up, once set and locked then just keep an eye to ensure nothing slips over time.
Benchdogs guides £132, Fc tools £130 Woodpeckers in a case £560 TSO at £375 Senaca at £238 Banggood £ 94
In reality with just £38 difference then I would buy from Benchdogs.