U.v. negatives:
Heated up water
Tube must be cleaned at l east every 2 weeks.
Buy new tube every 3 to 4 months
Water flow must be within I've spec flow
Continuous electricity usage
What's your source of info? Keep in mind specs will vary greatly between models and manufacturers.
Yes, UV sterilizers perform better if clean - just buy a model with a wiper. It costs a whopping $15 dollars more than the standard model.
Heated up water - negligible for most tanks. I use pinpoint temp probes and have tested with and without the UV on and haven't been able to observe a difference.
New tubes ever 12-14 months for the model and manufacturer I have... never heard of a 3-4 month life span.
Yes, water flow is the 1/2 the equation for UV dosing. Not hard to figure out with a pump head-loss calculator which costs nothing.
Continuous electric usage - true, but negligible again for most tanks. My UV sterilizer takes 1/10th the wattage my return pump does for example.