I am particularly pleased with the TurboTwist line of UVsterlizers. They are not necessarily the longest lived or built like tanks, but they are easy to use, easy to service and the engineering of the unit is actually a very elegant thing.
I have other sterlizers that are higher rated and supposedly last a lot longer between bulb changes and do a more efficient job of sterilizing, but, in the smaller sizes (for tanks under 100 gallons or so) they are not efficient or elegant - nor do I believe they actually do as good a job. To make them small enough for smaller tanks, the main house where the water dwells is short - and the water is tapped into the side. This leaves pockets of stagnant water - and actually only a small area where the water is sterilized. Larger units for larger tanks are, indeed, more efficiant than the Turbos - both in cost and function, but the smaller ones simply are not designed well.
In the Turbos, the water is circulated around the UV bulb - leaving no pockets and in reality, a fair sized volume of dwelling water in proportion to the actual unit.
The smaller, pre-plumbed unit from Goldfish Connection is a fine unit, but it is a bit small for a fully stocked 40+ gallon tank. I would suggest looking into a Turbotwist - they are extremely easy to plumb, using standard PVC stock from your local hardware store - I think I spent about $5 for the pieces on the last one I installed.
JMO
Check out this marvelous thread....
http://www.kokosgoldfish.invisionzone.com/...showtopic=34785