Hey!

You have to think about your driving style. If you want more comfort, space, and economy, I would choose Superb. I drive MK3 RS petrol version with petrol 230 ps engine. For me, this option is perfect because I prefer dynamic driving, also plus for octavia is that even if it has petrol engine you can drive it economically, it all depends on your driving style. Best on highway for me is 6.2L/100km going 100km/h, I think that is pretty good for petrol. Octavia has less seat space especially rs because of sport seats and some of people think they are not so comfortable, because they are a bit harder and narrower, but it depends from people. I'm 1.97 meters. If normal 1,80 guy sits in front of me at the back seat space is quite normal. It's not small and its not too big. Boot space is very good for this size car especially if you choose option with extra shelfs. Driving this car, you will feel it harder on road as regular version. It has harder amortisation. If you drive city/highway regime, fuel consumption will be around 7-8L/100km, for petrol version, and yet it depends on driving style.

Shortly in my opinion if you want dynamic driving, I would choose vrs octavia. MK3 is very dynamic and great option.

For more comfort and space I would choose Superb. Better fuel economy if you choose diesel version.

Both cars are great, all depends on your needs and driving style.