I use a few based on what type of event I'm doing and the type of material I need to play.
VDJ is very intuitive if you have good computer skills. It's a great software to put in front of beginners because they have no trouble understanding what is going on. It does require that you put a few things into human memory, or adjust the settings to certain standards. (For example, there is no "eject" button on the native skin.)
Serato I like because it's features are more inline with what you want in club mixing, and it's sync lock functions quite well in that domain. It is the product most likely to be found installed or supported in a club (controllers) masking it a must-have if you move around or collaborate with other people and vendors.
OtsAV is outdated and it's video rendering method is no longer supported in post XP versions of Windows. Video is unreliable in Ots and on Laptops is often non-functional. I will use it only for music at corporate events, background music, or anywhere that predefined music playlists are utilized. It is designed for automation (unattended play) and is not that great for live DJing or mixing. It does not cue or instant start with same the precision that other softwares do. The skin is crowded and crammed. Licenses are too restrictive, and price is comparatively high given the lack of features. Music management is great - but, you will have to work within the proprietary .ots file format to take full advantage of it. I use hard drives containing libraries in both the .ots and mp3 format to make changing software choices as easy as opening a new application. Ots can run simultaneously with MS Powerpoint which is handy in a corporate AV setting. (So will some of the others.)
MIXX (open source) resides on all my backup laptops and karaoke systems. It is about as functional as VDJ sans some controllers, and I would recommend it to anyone who can not afford to spend money on the other brands. Because it's open source - you can install it anywhere as a backup, or carry the setup program with you on a thumb drive to install on any machine available to you.
CLUB DJ Pro is something a friend of mine swears by - and it seems to be quite reliable for him in both audio and video play. It's price is also a steal for such a full featured DJ sortware. I'm personally not a fan of it's skins (layout) so, I no longer have it installed anywhere.
TRAKTOR is probably what I would use if I still did a lot of club work or really wanted to go deeper into mixing again. It's the expansion possibilities that make the learning curve steeper but, if our musically inclined or have a studio IQ it shouldn't be hard to get exactly what you want from it. (You will spend some coin to get there.)
ABLETON is where the studio meets the DJ. It's a great combination of creative tools and DJ play. Would love to use it but, rarely have the type of application anymore to justify it.