DF is probably better for customers who want to pay for English subs, in certain parts of the world and only there, and they want them fast.
Viki and DF provide different things, so people slamming Viki for something that it isn't required to offer is the issue here. It's a different business model. For some reason, this simple truth just can't get through to some people.
It's not like Netflix that chose to expand in Greece but refuses to offer Greek subs in almost anything. They just expect viewers everywhere to put up with "English only" subs, which is indeed infuriating. But I digress.
There's a thread l think about instances of Viki-paid subbers contributing to projects. It didn't really go well.
By all means, everyone should subscribe to the provider that fills their needs.
But you can't require someone to change what you've already agreed on and bash people's efforts, just because someone else offers something that suits you better. Just go to the other person and be done with it.