Vato
I'm hardly an expert when it comes to UV filters. I do have an 8 watt Angstrom hang on the tank unit. I wanted the 4 watt variety but the Aquarium Center in Baltimore was sold out. The unit I purchased was about $96, if I recall. Again, I've only had mine for a little over a month, but I can tell you that my tank was cycling when I put it on and that the cycle completed without a hitch.
I purchased it as a safety precaution for a tank in which I plan to keep discus. I read a few articles about uv filters, talked to a few people, and, like yourself, sought the advice of people who owned them. I did not get any negative feed back, but I agree that you don't have to have one. I've kept many different types of tropical fish for many years without much of a hitch and WITHOUT using a uv filter.
I purchased the hang on unit because I wanted to be able to move the unit between tanks in order to reduce the number of water born pathogens but NOT to fight algae. I do that by keeping phosphates at a minimum. I have two tanks currently, but I hope to add a 125+ tank in the next year or so. If you get a hang on uv filter you'll also have to purchase a powerhead and a few feet of tubing.
Also, If you do not fill your tank to the top the hang on unit will empty water into the tank causing serious surface agitation. This might be a concern if you put this particular unit on a planted aquarium with a low water line. This might help you decide between an inline unit and one that hangs on.
In line units are installed after the filter such that water flows from the tank to the filter and from the filter through the inline uv filter and back into the tank. I imagine you could put it anywhere inline, but it seems logical to put it after the filter to cut down on the debris that will collect the surface and reduce the transmission of uv light. In line units do not require a powerhead. However, they could be configured in a similar manner as I have described for the hang on unit, using a powerhead.