I have a couple of zhanchis, a fangshi (V1), a huanying and (now) a weilong. Here's my 2 cents worth:
Fanshi
Scratchy out of the box, but becomes smoother with breaking in. Smooth and consistent, without the clickiness of a Dayan cube. Cuts corners like it's going out of fashion. HORRIBLE stock stickers. Replaced with 1/2 brights, but I've not used this cube a whole lot. The plastic feels cheaper than the Zhanchi, and the build quality isn't too impressive. It struggles to hold its cuboid shape, if you hold two corners in your hand and shake, which translates to flimsiness when solving. Has a tendency for corner-twists on looser tensions.
Huanying - my least favourite. The plastic feels really cheap, and the cube feels hollow and brittle. It's noisy as hell, but cuts corners even better than the Fanshi. I get the impression that this cube was designed to cut corners, and nothing more, because so many reviews go into detail of how far a cube will cut. But we all know corner cutting isn't that important in a solve - if you're 45 degrees out, you need better turning accuracy, not a more forgiving cube! The stickers are the best thing about it. Apart from the orange, which I don't like! I can imagine this cube being hella-fast if you don't mind the fact it sounds like you're cubing in the middle of a heated Mah-Jong tournament.
Weilong - I've only had my Weilong for a few days, but I like it. It's like a slightly quieter, more developed Huanying - it's made of the same plastic, which I found a little disappointing, because it still feels cheap next to a Dayan cube. It's still a little noisy for my taste, but I've been spoilt with my Dayan cubes. The stickers are great, as with the Huanying (other than the orange!), and I like the MoYu core, it's pretty! I sometimes find I over-turn in LL algs with this cube, but that's more me than the cube. I've not had a single pop in a few hundred solves. I'd have had a few with my Zhanchi in that time. I'm pretty sure this will share my 'main' spot with my Zhanchi, once I get used to it. It's practically unpoppable, but I'm not 100% sold on the feel. I think if they made this cube out of a slightly more expensive, or slightly thicker plastic, it would be truly great.
Zhanchi - great cube out of the box. Once modded, can be quiet, smooth, and pretty much unbeatable. Feels solid and well-made, but has a tendency to pop on loose tensions. Mine has 48PEM and some rounding of the edges and corners, but not CPM, and it's a thing of beauty. 55mm of pure silky-smoothness. I sometimes get lockups in LL algs with it, maybe more than on the Weilong, but again that's me rushing.
The verdict: despite the flurry of Dayan-toppling cubes that have recently been released, I don't think any of them have a case for becoming the #1 cube out there. There will be people who love the Fangshi, and people who love the HuanYing and, I suspect, even more people who love the Weilong, but if someone came up to me in the street tomorrow and said "I'm looking to get into speedcubing, what's the best cube available", I'd still have to say the Zhanchi.
Happy to be proven wrong by the Weilong over the next few weeks... we shall see.
@Lchu - do you think the Zhanchi spring swap has made a significant difference? The only shortcoming of my favourite Zhanchi is the pops, but I've never considered swapping hardware.