I have both SEIO and Tunze - and like both. SEIO gives you wider, softer flow, rather than a harsh, direct jet of water that traditional powerheads give you.
SEIOs have pretty well shaken off the stigma Rio has on pumps. However, there are still reports of some pumps having issues on restart. When the power goes off and comes back on, the pump may not come back on. I've had SEIO for about a year, and have had this happen twice. It's simple to fix. If the pump doesn't restart, you just need to bump the impeller with your finger to get it going again.
SEIOs are relatively cheap for the flow the produce. The craftsmanship isn't top notch like Tunze, but they are good for the price.
