No offense, I used my First Generation iPhone along with my Sena Ultraslim for almost 5 years. However, Leather pouch didn't protect with it off the case.
I changed to iPhone 4 White last year. I really liked almost-naked case to show how beautiful iPhone 4 White is. I decided to go with Snap-on Case, two of Clear Power Support Air Jacket Case, Incase Snap on (Clear), and Incipio Feature Clear. PowerSupport and Incipio have the same problem, its durable last only a few month for my use. Incase Snap on that I got is kinda knock off, fitting is the problem.
I am tired and sick of changing plastic case for almost everything 2 months, I do research for better alternative. At first, I looked for rubber bumper style case. Yes, It have cheap alternative starting at $ 1.- to $30.- but most of them will end up loose up or discolor (I like my phone to be "White").
Finally, I ended up buy Element Vapor Pro White edition from Element Case website. It is very nice case with small barely notice signal degrade. But it looks beautiful. However, the shape of case causes problem for my iHome Speaker. I fixed it with Radtech dock extender.
However, I started reading in this forum. I found Xtrucase without any screw to attached. I ordered white pearl since it cost half of vapor pro. I try for two days and yes, signal degrade is not so good due to many factors. One of them is inside pad of the case that I contact Xtrucase and they are kindly enough to set 2 sets of new pads.
The button line is all the choice depends on individual. Some like more protective case, Some like to show off iPhone, Some like belt-clip style. And yes, some cases create headache to one user and like god send to another user. For me, my choice is Aluminum case from durable and looking good (for me) point of view.
PS. In theory, Metal cage can cause signal degrade. However, there are many factors on "signal strength" such as Position, In-phase and Out-of-phase from Multi-path fading, Shadowing from large structure and so on that can improve signal strength. Also, Metal case connected with antenna can act as antenna, it can "help" or "destroy" signal strength with proper length.