The big version gets more lumen but it also gets costlier substantially. In terms of functionality there's no difference though the runtimes are much longer thanks to a bigger battery
All Knog products have a 2-year warranty from date of purchase. We will cover defective hardware, software faults & factory defects. We won't cover ordinary wear and tear or damage caused by improper use or accidents. If you believe you have received a faulty item, please complete this Warranty Form. If we can't resolve the issue, we will arrange for a replacement product to be sent to you. Do not go through the returns process (below). From- www.knog.com/pages/returns-warranty