I have owned them all. Like said above, the GoPro can get expensive quick. Batteries, SD Card, and Mounts....they all add up! If your track doesn't have good lighting the GoPro will be a big dissappointment for you! It's not the good in low light, in fact, it's terrible. The Vholdr is a great camera, but also pricey when it comes to buying what you need, plus research the problems they have had with it. The Small wonder is a great camera, but mounting can be difficult, time consuming, and ineffective at best.
We tested all of these at some point, took them apart, researched side by side, and took the best pieces of all of them to make our own system. We sell this system and have been for quite some time. You get EVERYTHING..No buying mounts or sd cards, or fiddling with duct tape and zip ties trying to hold a camera designed to film little Timmy's birthday party.
I went to school for 4 years in Television production with a Bachelor's degree and have worked around cameras most of my adult life. We have designed, tested, and built a system that gives you good footage everytime and lasts longer than anything else. We have raced mini-sprints for several years and know what it takes. We have flipped it on full size sprint cars, jumped it on ATV's, and even watched as it took a gasoline bath. It works great in low light and can take the abuse, rocks, vibration, and mud that it will see every weekend. It's affordable and comes with GREAT support directly from our company. We have sponsored Maximumdirt several times and they even own one of our systems. Several Sprint car teams use these including several on the WoO tour. Check our system out today, we even have low light videos and wrecks on our website for you to enjoy.
http://www.SportActionCam.com