If you, like me, are considering both the silicone and the clear plastic protectors from this brand, this review is for you. I was given both for review and will focus on comparing them.
The clear protector is made of thin plastic that comes in a top and bottom piece which snap on and off easily (no damage). While it looks dark in some pictures, it is transparent. Some have commented on the little spots of condensation under the protector, which don't bother me at all. I imagine these occur with any protector, but are evident in the clear ones. In terms of protection, the plastic is not going to protect against major impacts. Rather, it will prevent scratches from normal use.
The black silicone case comes in one piece and slips on and off very easily -- important because it blocks the SD card slot. It looks just like a silicone case for a phone, which is good or bad, depending on preference. I think the clear case looks better. The silicone has a nice feel, but it makes the system more difficult to slip into my pocket for Streetpass action. The silicone also covers the shoulder (top) buttons, which makes them a bit harder to push, but is good protection. These buttons are exposed with the clear protector. As with the clear protector, it only offers scratch, not impact, protection.
While both products are thin, they have enough thickness to prevent using the charging dock. I really dislike this, and it could have been remedied by including a larger dock. I can't imagine this would cost them much, since the docks are just plastic with contact pins. The clear protector can even balance precariously in the dock and work. The silicone case has a band which covers one of the dock connectors, though I'm sure it could be cut a bit to make room for the pins to connect.
A widespread complaint is that the lid of the 3DS closes too tightly, allowing the analog stick and bottom screen to make marks on the top screen. The clear protector does nothing to address this, but the silicone protector sits inside the lid a bit, adding enough extra space to fix the problem. I think this was total luck on the part of the manufacturer, but it is an elegant solution if you plan to use a protector anyway.
Overall, both protectors are very high quality, with a nice fit that is far superior to the ultra-cheap alternatives. I prefer the clear case based on aesthetics and pocketability, but the added screen protection of the silicone protector has made it the permanent solution for my 3DS.