You would think that with double the amount of Cores the Octa would far out perform the Quad Core Processors any day of the week. That seems like a logical assumption. However, it's just not the case. There have been so many tests and comparisons done with both Processor types and the results are mostly always the same.. Worlds apart? Hmm, not quite.
There really isn't much difference either way. Some tasks were slightly more efficient with the four and some were a tad better with the eight core set. Heck, some of Apple Dual Processors are superb, but most people turn their nose up at the very sound of "Dual" these days.
The Trade Off
8 Cores use up more power than four. With that in mind, and with so many guys and girls wanting a long battery life, it's not really worth the extra money to buy something with Octa technology. The differences in performance are too minuscule. But saying that, the differences in power consumption between the two aren't all that far apart either. People are always running on low percentage battery in Tablets and Smartphones so I suppose that extra bit of energy juice is quite important.
The structure of both chips is very different, and the Quad uses its resources more effectively. The Octa is just two sets of four Cores squashed onto the one Processor. So what it does is use one set of 4 to run lower energy tasks and then calls upon the other 4 if things get heavy, like you start playing resource hungry games, a thousand browser windows or launching complex Apps. As of today, a lot of applications don't actually take full advantage of the eight anyway.
Best choice? That all depends on what you do with your device. Some love to have the latest new thing, and that's great, but its not really needed here. For most of us, doing all the normal things on our device like gaming, youtube, browsing the Internet etc, the Quad is generally the best option. Its more than capable.