This is actually a hard question for me. It all depends on the way the warrens are analyzed. If you want to know what warren I would want to live in, it would probably be Watership Down, but

s warren is nice too.
But the fact is that Watership Down seems like a boring place. Nothing exciting happens there. When there isn't a war going on, anyway. But the fact remains that during times of peace, it would probably be boring. So what would be the most exciting warren?

s warren is interesting, being in a maze and all, but really, apart from that it seems ordinary. Maybe it isn't. Maybe it is very exciting, but since it doesn't appear in more than two episodes, we don't really have a chance to find out.
Sandleford warren is unusual. In the series, it's never seen, only mentionned, so you really have no idea what it is like. In the book and film, it seems like the average warren, with its share of elil and everything, not particularely safe nor particularely dangerous. It has nothing special about it.
Efrafa? The book and series versions of the warren seem very different from each other (the film version seems like that of the book with less details). In the book, it is well hidden and very overcrowded, with the marks and a very competent owsla. It may be a nice place to live in if you don't care about the dictatorship. It can be rather exciting if you're in the owsla, with all the wide patrols.
In the series, it's this great big hole with a big dead tree. Not very well hidden, is it? Also, it doesn't seem to be very overcrowded, as

and

have a large burrow to themselves. The owsla doesn't seem as competent as in the book. Also, as

pointed out in Kidnapped (?), the rabbits are not healthy and if disease breaks out, they will all die. Not really a nice place to live. But all this contributes to the atmosphere, which is much more mysterious and scary than in the book.

s warren is quite a warren, with their shapes and singing and greetings and

. It is also probably the most dangerous warren of them all. In Darkhaven, sure you may be forced to fight for your life, but at least you have a chance. Here, once you're trapped in the wire, you will die a long and painful death since nobody around will want to dig out the peg. But the atmosphere is really creepy in all three adaptations. So yeah, it has a lot of potential.
Speaking of Darkhaven, it's really unusual. It doesn't even seem to be a warren, strictly speaking. There are no underground holes or tunnels, as far as I know. Why rabbits ever repopulated this place, I have no idea. While it only gets introduced very late into the series, it is extremely important in these few episodes. It also seems like a very "exciting" place with all the fighting, the conveyor belt and all the other human machines. But this excitement comes at high price. It's not really a place where I would want to live.
Redstone seems to have a habit of getting destroyed, first by the great sickness that kills everyone except

, then by the humans. It also would have had a third destruction, by the elil if

hadn't arrived, and a fourth time, by

again in The Stand. But there doesn't seem to be anything really special about it. It's just a bunch of rocks that aren't even red until season 3. The first time it is seen in The Vision, it's in very bad shape. In The Roundabout, it gets cleaned up but remains uninhabited. In The Stand, the rabbits arrive there to stay, but that's not the most important part of the episode. In

s Way, it seem pleasently boring. I've already talked about season 3.
Finally, I guess maybe the poll should also include Vleflain. It's the half-Watership, half-Efrafan warren that gets established in TFWD. Unfortunately, I haven't read TFWD, so I can't comment on it.
All right. Let's simplify all this. Watership Down is where I would want to live, Darkhaven and Efrafa-book are the most exciting, Efrafa-series is the most mysterious, the warren of the shining wires has the most potential and the maze warren is underused. Sorry about the wall of text.