These are regular cvd's, which are not bad.
The outdrive cup connecting to the U-joint will have a slightly larger inside diameter, but it is identical in anatomy to a cvd, which will allow you to maintain constant uninterrupted velocity up to a certain angle - and at 45' to 55', there will be plenty of interruption. Even at 35', a regular cvd is going to start chattering at high speed/high load. These were revolutionary to RC back in the early 90's, where dogbones were the norm, and standard universal joints were still very fragile. The large outdrive cups of CVD's provided better protection, and the ability to perform maintenance/reconstruction. And nobody needed to use 45' steering on a regular basis. This model that you quoted will alloww your car to hit that angle (so long as castor blocks and linkage allow it). But it won't be very comfortable or sound pretty at high velocity.
Enter the double cardan joint (double U-joint)
This has a different anatomy:
http://www.rcmart.com/3racing-drives...Path=1102_1106
It's essentially two universal joints (aka: cardans) on a single driveshaft. Imagine having a second wrist between your hand and elbow. A person could pick their nose at all sorts of new and creative angles. Likewise, it provides new rc cars with the potential for greater angles of uninterrupted steering (so long as the castor blocks and steering linkage allow).
Although not a necessity by any means, they do remove a lot of the "chatter" that full-tilt steering provides.