Which is the best processor for asus eee pc t91?

First of all, the speed comparison, some i3s are quicker than i5s, but, an i5 can handle more processes. But definitely Intel Core i5, the new I-Series processors are very complex. They have a feature called multithreading that allows each core to emulate 2 cores. Therefore, a dual-core processor can carry out 4 tasks at the same time. It's basically a quad-core. They are also typically much quicker. Intel also is supported more among operating systems and some software’s. If you plan on severe gaming, than an i7, hands down. Definitely the most composite, quickest Processor Intel makes at the moment, available in a standard computer. So at last it depends upon your pc and for you i think these processor are the best just look at what you need in your asus eeepc t9t.