Actually the POCO meter base TVSS are one of the best you can get, plus come with a pretty rock solid guarantee. In my area they come with a $50K guarantee of major appliances like HVAC, motors, refrigerators, and exclude point of use electronics. For that they offer Class ?A? point of use devices. What makes the POCO TVSS devices attractive is there is no better place to have one installed, robust in K-Amps per mode, no lead length to connect, and no ground is required, not that ground has a darn thing to do with a surge.
Not all TVSS devices are created equal, far from it. As Tom mentioned you get what you pay for. The next best devices are those with TVSS built into the main panel. Like the meter base units there are no leads involved, so the SPD?s are bolted right onto the bus. The down side is the cost, as it adds hundred$ to a panel for a quality unit. Like the POCO units most of the better ones come with a guarantee.
On the bottom of the food chain are the add-on units to a panel or aka parallel units. These come in all types of flavors and designs from the little cans that screw into a knock-out, to a utility box that mounts next to the panel. Their effectiveness ranges from useless to moderate protection.
Beyond the service entrance you need to have point of use devices installed at each location where sensitive equipment is utilized. These range from term strips to receptacle outlets. Again quality varies wildly from poor to good.
One really needs to understand the ratings, listings, and technologies to identify the dogs from the winners. I can help with that if needed.