When you consider that nothing will protect your from a direct lightning strike, having something that provides you with replacement insurance might be worth the extra $$
If your only concern is with spikes, brownouts, or loss of power then most non-brand names would suffice just be sure to research on them to make sure they are able to actually do work / have what you want.
The difference would be the quality of the internal components.
If you really need one then try to acquire a branded one. It's main purpose is to save you from mess when things go wrong (power failure, lighting, surges, etc). It would be bad if the UPS itself is the one who fails along the way.