Basic Question about UV Digital Copies

[hbarnes]

First off, let me say that I prefer iTunes copies to UV copies, but often UV is the only option you get.

Here's my question: why are some codes "only VUDU?" I've come across ones where it redeems through the publisher, such as Sony, which is reasonable, but for example my UV copy of "Vice" only plays through VUDU and shows up as "unavailable for playback" on Flixster, my preferred UV service.

Second part of that question: what's the benefit to VUDU over Flixster? It has an atrocious UI, and isn't really that enjoyable or easy to use. Plus, their HDX system is pretty misleading, considering that the only other option now is SD. I like Flixster because of its simple interface and easy workability, but why do so many people prefer VUDU?

Any answers would be appreciated. Thanks.