Actually, the DV 5 Encode from the streaming services is the best quality they can offer.
This has primarily to do with the “premium claim”. Dolby Vision is supposed to catch people, so it is supposed to attract new customers.
Depending on where the releases come from, HDR10 and DVP5 are also realistically identical from the bitrate.

For TV shows/series you should go with DVP5.
For Movies you should go for the version with highest Bitrate and DV, no matter if Hybrid injected DVP8 or retail untouched DVP5/DVP7.

Thanks. But why would the profile 5 a higher bitrate? Is it just MAX have it like that on their servers?

Dolby Vision Profile 8 is really useful if you want to create something that is only available as a DV source on the web combined with a UHD BD / HDR 10 Remux.
An example would be the Disney UHD Remuxes which usually come without DV, but there is DV on Disney Plus. These hybrid remuxes are then “the best of both worlds”.