I hope the post heading didn’t deceive you. You see, there is no such thing. Lets see what our options are:
Azureus - the Windows Vista of torrent clients. This is what I use today. Every time I start it up, a piece of me dies. This thing has one thing going for it and a million thing going against it. What’s good about Azureus is that it actually works rather well. Download and upload speeds are generally very good and the client is friends with most private trackers. It also supports all the bells and whistles of the Torrent world such as DHT and encryption. Now, the issue with Azureus is what I hinted at when I compared it to Windows Vista - it’s a resource hog. Not only is the application itself immensely complex and bloated, but to make matters worse, it’s Java. That means you have to live with the overhead of the Java virtual machine whenever Azureus starts up.
The fact that it’s Java usually means another thing, it’ll look like hell. I have yet to encounter a Java application that looks good on OS X or Windows. The applications sometime try to mimic the widgets and controls of the operating system it’s running on, but it never quite looks right. In the case of Azureus, they haven’t even bothered to make it looks remotely Mac:ish. Don’t stare directly at the following image, it might cause permanent damage.

What the hell happened there?
Moving on. The next client on the list of potentials in Transmission. It’s actually a rather nice client with a solid looking UI and a decent feature set. My issue with Transmission is that I just don’t get the same speeds as I do with Azureus. Download speeds are pretty much the same, but for some reason, it won’t upload anywhere near as much as Azureus does. The UI is nice, but I’m not a big fan of the main listing where each torrent takes up a lot of screen real estate. When you have 30 torrents in the list, it quickly gets difficult to get an overview.
Next on the list is XTorrent. This client is arguably the best looking client I’ve ever seen. Good looks aside, it has a few issues. First of all, it is based on libTransmission (the torrent library used in Transmission) and most likely has the same speed issues as Transmission. Secondly, it costs $26. I have no problem at all paying for good software, but before I do, I like to get an opinion of how well the software works and that’s just not possible with the unregistered version of XTorrent. It’s severely limited. Lastly, the person behind XTorrent, David Watanabe, has a reputation for being a real a**hole and that just doesn’t fly with me.
Finally, we have BitRocket. BitRocket appeared on the scene a little over a year ago and personally, I thought it looked extremely promising. That being said, a little over a year has passed and not a lot has happened. The website is, should we say, spartan and the forums have been down for some time. I’m not sure if the project is abandoned or what is going on, but this doesn’t bode well.
Apart from the 4 clients I’ve mentioned, there are a few more. The only two I can think of right now are Bits on Wheels and Tomato Torrent. Nothing I would recommend though.
What the OS X world needs is µTorrent. The developers claim that a port is still in the works (nice forum software btw), but this song and dance has been going on since 2005 and I’m starting to doubt whether it will ever happen. You can run µTorrent in OS X using Darwine or CrossOver Mac, but that’s like hooking up a caravan to a Ferrari.