It depends completely on the deck. One person in this conversation might say it's bad because they're running a deck it's bad in and the same can be said for those who think it's good. Here's how to tell:
1. Dedicate the same amount of spots for the Supporter whether you choose Cheren or Bianca. Let's say 3.
2. Put in a backwards card.
3. Playtest with somebody who understands this concept and is okay with you doing this.
4. Every time you get one, write down wether or not you'd rather of had Bianca or Cheren.
This is just one idea. Just try and figure out for yourself which one is right for you instead of drawing "party lines" and going diehard one or the other.
Now, back to deck choice. If your deck is mostly things you can burn out of your hand (trainers, basics, energy accel?) then go Bianca. Right now I'm testing Blastoise, so obviously I'm going to use Bianca because I burn my entire hand out in one turn. If you're running something like Gothitelle/Gardevoir, then you'd use Cheren (since you don't burn cards as fast).
In addition, as far as Juniper goes, it's not as good as it was in HGSS-on. I think we'll have to start spreading our Supporter lines out instead of running 4 of a supporter. I'm currently trying out 2-2-2-3 of different supporters, which sounds inconsistent, but when you look at the big picture I'm still running 9 draw supporters. I've also got in 2 or 3 Random Receiver to fetch the supporter that will do me the most good. (ex. If I only have a Juniper in a big, dead hand, use RR to try to get an N. Or if I only have a Cilan *which I didn't include on my supporter list* and want a fresh hand.)