Hi,
I had bought around 10 power banks in previous 2 years.
High capacity power banks are not good. They will not last more than 1 year even if you are a good care taker of your produt.
Power banks of Capacity less than 6000 mAh are always good. I recoomend to buy lower capacity power banks.
If you will talk about brands then Intex or mi is far more better than Syska. Syska power banks are taking double time than usual to charge and there rate of charging is also very low.
I hope you this article will help you in making a fare choice about Power banks.