I don't know much about UPS but now I must decided to buy new UPS for my company.
I read from somewhere more power FACTOR is better than less power factor.
But I'm not sure about that because some expensive UPS has less power factor than cheap UPS.
For example product A price 50 USD is 850 VA and 385 Watt then power factor=0.45
Product B price less 50 USD but it is 500 VA and 800 Watt then power factor is more than 1 if I'm not wrong power factor must be between 0 and 1.

I'm not sure now I should but A or B.
Please help me.
Thanks for your help.Where did you get this notion of a "power factor"?  And, exactly what models are you referring to?  I've never seen mention of a "power factor"; I just looked at some unit from newegg.com, a major online seller of computer components and accessories, and the specifications on them mention no such thing as a "power factor".

I can't ADVISE you on specific models or the VA and Watt ratings.  All I can say is I've used an APC, model Back-UPS ES, for several years on my main computer and it's worked fine.  I have done one battery replacement since I've owned it.