I bought a Lenovo for my girlfriend (S820), since Moto G was sold out. While it's a pretty decent phone, the UI has some lag and feels a bit sluggish compared

I bought a Lenovo for my girlfriend (S820), since Moto G was sold out. While it's a pretty decent phone, the UI has some lag and feels a bit sluggish compared to its competitors. I think the Mediatek does not deliver the same performance as other similarly specced chips. I don't know enough to understand why, maybe the GPU is not good enough or something. Edit: someone says that, among other improvements, Motorola uses a different and faster filesystem (F2FS) which is faster (https://news.ycombinator.com/item?id=7742608 https://news.ycombinator.com/item?id=7742608). It does have some big advantages (much better camera for example), and the battery seems to be pretty good too. Huawei has ever cheaper similarly specced phones, but the reviews scared me, it seems their software is extremely buggy. If you're considering rooting / modding your phone, then maybe one of these phones is a good option.