Hi I have tried free trials of both. Both were easy to signup and use. The similarity ends there. I liked yupp tv better and now subscribed it, using for 3 months, so far good. Did not experience connectivity issues. Pricing wise also it is good, with more channels for less price than sling. They offer good discount for yearly or 6 month package(I have subscribed monthly package only). Also yupp tv has 2 separate streams for major channels like sun , k , jaya. One stream runs in India time and another in US time (I did not have this feature in sling tv trial version). Signup for a free trial for both and evaluate yourself.
I tried yupp tv recently because I wanted to get it for the inlaws when they visit. No problem with the connection or quality , but the content was terrible , so disconnected in a month.