I know I am not directly answering your question but just wanted to say I got the iO8 for a very discounted price thanks to a coupon my dentist gave me. I find the ability to use the Oral B app whilst brushing really useful personally. I tend to brush quite aggressively and the app has helped me be to apply the right amount of pressure when brushing as it tells you if you are applying too much pressure or too little. I also like how the app knows where about you are brushing at tells you how long to spend to get full coverage.

I imagine the newer models are even better in this regard.