Why go with a true online ups ?
True online ups systems provide complete protection with very few drawbacks. There are three main reasons we prefer true online versus standby and line-interactive.
First, Power Quality - True online double converison ups systems provide super clean sine wave power at all times. They regulate output voltage at +/- 3% or better.
Second, They have zero transfer time when the power goes out. You equipment doesn't even know the power went out.
Third, modern true online systems do not use a transformer so they are lighter. A line interactive ups has a transformer in addition to the lead acid batteries - What a pig !
The only major drawback to true online systems is that because they are running on the inverter at all times they are slightly less efficient. However, most of the newer designs include a Green mode you can use if your power quality is pretty good.
A couple of examples of true online ups systems are:
Orion Power System's Online RTX
the Eaton 9130 Series