I've had both. I currently have an Octavia estate, previously had a Golf estate, previously had a Golf estate, previously had a Fabia estate, during which time DH had 2 Octavia estates.
They are very, very similar cars and none has ever given us any problems. The Golfs were a TDI and a petrol BlueMotion, the Octavia's have been TDis and the iv hybrid. One of the Golfs got rear ended twice and we were unharmed inside. I'd certainly buy again!
The Octavia is a bit longer in length; this space is in the boot, so the boot is a bit bigger. The cabin space is pretty similar, but I don't have the measurements to hand. This might be something to check out for ERF seats (we didn't have them, my dc are just a bit old for when the law changed).
Both cars have been great. I only changed because my car came with my job, and I'd happily replace it with the most similar I could each renewal.
We've been camping for a week with bikes (on the outside) in both... but the kids were pretty small then. They are great workhorses for heaving around kids, teens, cricket kit, work stuff (construction site), motorways, not too big to park... There's really not much to choose between them. And they were all serviced by the same VW dealer.
You do get more for your money with an Octavia, but the Golf estates hold their value really well and have a lot of stuff as standard.