All of the APC UPS's are good quality. What you are paying for is the size of the batteries in the unit and how much power they can put out when the house power goes off. The batteries are kept charged as long as the unit is connected to the wall plug. You use the switch on the unit to turn off all devices plugged into the UPS.
When there is a power loss, you will hear the UPS beep as it takes over supplying power to the units plugged into it. It will switch back to line power as soon as AC power comes back on. The size of the batteries and how long they can power your system is what you are paying for. The batteries represent over half of the cost of the unit. For example I have two older APC units that worked very well for four years before the batteries wore out. The more power outages you have, the sooner they go out, just like a car battery. The unit cost $90 when I bought it. However, to replace the two six volt batteries in it cost me $46 at Lowe's, and these replacement batteries will only supply power for 80% as long as the more expensive one originally supplied by APC.
For a typical system, monitor, printer, router and modem. Either unit will work well and supply power for 15 to 20 minutes or more if necessary.
I recommend everyone get a UPS for their computer. It protects it during power glitches. Most users do not need an expensive unit. The $30/$40 APC units sold at Office Max/Depot and Costco and SAMS will run typical systems for five minutes, long enough to shut them down.
Most newer APC units have a lightning protection filter for dial-up phone line that is useful for protecting your modem. The Cable modem jack will help protect your Cable modem should your outside grounding block fail. But I would not let that feature effect my choice of units.
