To some extent I believe you "get what you pay for" including with UPS's. At one point I bought three Cyberpower UPS's (Cyberpower is one of the most inexpensive UPS brands in the U.S.) Each of these failed (would no longer supply power to the battery backed outlets, after power was restored) after two or three major power outages of 6 hours or greater. Many businesses in the U.S. use APC's. I now try to buy APC and Conext (Conext is manufactured by APC) and if I am looking at another brand I always look for reviews.
No matter what you end up with I strongly suggest you get one with AVR (automatic voltage regulation.) A UPS with automatic voltage regulation always keeps the voltage within a specific range. If the power drops below that range (called a brownout, but the power can still be on) or goes above that range the UPS kicks in to lower the voltage, or add voltage from the battery to keep it within that nominal range.