Let's start back when I was a young teenager in the late 70s. There were four music papers around then: (from memory) Melody Maker, Sounds, Record Mirror and the NME. A friend of mine subscribed to Record Mirror. On the letters page there was discussion about mods and rockers; this was the first time I'd heard the terms. I didn't know anyone who would fall in either camp, but being rural Lincolnshire this isn't a surprise. Another friend was embarrassed to discover that his dad used to be a Teddy Boy. Although his dad was middle-aged then, I did the maths and it was entirely plausible that he was a teenager at the right time.
The music I listened to and liked around then was the Specials and Madness, and not Shakin Stevens. If someone had made me choose then I would have said Mod.
When we moved to our current house and I was no longer able to walk to work, as I had done for almost all of my previous working life up that point, I got a 30cc scooter. I could ride it on a normal drivers license, after I took the CBT. After 3 years I upgraded to a 125cc motorbike and took my full bike test. As well as being more (but not very) powerful I preferred the riding position on the motorbike (though I once did carry two dwarf apple trees on the scooter). So if someone had made me choose because of transport criteria I would have said Rocker.
Then we move onto the Olympics and The Who playing at the closing ceremony. I knew My Generation of course, but I'd never really heard Baba O'Reilly. One of the band members was on Top Gear a few years ago too and they played "Who are you", which I'd never really heard. Even though my musical tastes went back to music released before I became a teenager, like Genesis and early ELO, I'd never really come across The Who. Finally I played them on Spotify shuffle a few days ago and came across "I can see for miles", which I knew but didn't realise was them. I really like all these tracks. So if I had to choose in the 60s I would have said Mod.
One of the differences between the two tribes was their dress. I'm not that smart, and I have been known to wear more denim in the past than I do now, so it would have to be Rocker.
So two all, what's going to decide it?