I used the yamaha version of the "my wedge" on my previous F115 and it seemed to work fine and was very convenient to use/store:http://www.simyamaha.com/Yamaha_Engine_ ... -ym-10.htm
I recently got a new boat with a F200 and it came with a transom saver bar from the previous owner. My personal belief is that you absolutely should use something, whether it is the wedge or the bar or scrap of wood, for two reasons:
1) If your hydraulics give out, you want something as a backup keeping your lower unit off the ground. At least for Yamaha's, that little support lever is not designed to be used for trailering and shouldn't be (unless your transom saver breaks and you have no choice) Also, see reason #2 for why your hydraulics are more likely to give out...
2) I know some may disagree, but I am fairly confident that the shock loads generated by driving over bumps and potholes can exceed (perhaps by a wide margin) the forces that your motor can generate and therefore you do need something to help mitigate these forces on your transom/hydraulics. To a large extent these are reduced by your trailer suspension, but adding some additional cushioning under the outboard (wedge) or supporting the outboard lower unit (transom saver) to reduce the moments generated by these forces is a good idea.
As to your question about transom saver vs wedge, I'm not sure. The wedge style or 2x4 is easy to use and nice and compact and resolves the first issue and part of the second issue, but it doesn't help with the moments generated by trailering and how these get transmitted to your transom. The transom saver, since the motor is supported on both ends, will reduce/eliminate the moments that are supported by the transom but may apply forces to your lower unit that are atypical at the contact points for the transom saver. Whether or not you think this is important depends on how severe you think the loads from trailering might be. I contend that the forces are higher, but the moments may not be. Since normal operation applies the force at the prop, that produces a significant moment on the transom (the lever arm is the total length of the engine). During trailering the forces act at the center of gravity of the engine which is probably much closer to the power head, so the lever arm is shorter. Therefore the moments generated during trailering could be the same or even smaller than those generated during operation even thought the forces are much higher. I suppose I would conclude that the transom saver is probably more effective but it may also be overkill and the wedge and/or 2x4 is probably just fine. In fact I may go back to the wedge style simply for ease of use and storage.