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's Dual (2) Processors are superb, but most people turn their nose up at the very sound of anything "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 Cores to run lower energy tasks, and then calls upon the other 4 if things get heavy. For instance, you start playing resource hungry games, open a thousand browser windows or launch complex Apps. As of today, a lot of applications don't actually take full advantage of the eight cores (Octa Core) 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.
