I'd go with 19's as well, personally I think that's the sweet spot for big wheels, big enough to look big and fill the guards (well on most cars) but not too big where you lose comfort, performance and pay a decent amount for tyres each time. I think some cars look ridiculous with 20s, usually stock older model cars with no body kit to help fatten up the car. Depends on car really, like take the VE for example that model looks normal with 20's on it because of how pumped out the guards look. I think what I'm trying to say is get the right sized wheel for your car to enhance the look of the car and not just get them because they are big. Right stance and right wheel choice can make or break the look of your car.
I nearly bought 20's for my car at one point because my factory 19's were damaged by the previous owner but I changed my mind at the last minute and ended up repairing my wheels and painting them gloss black. After that my desire to get new wheels slowly went away.
I think most of you have seen these pics in the last thread but I'll chuck them up again anyway.
How they used to look.
How they look now.
Now all I need to do is lower it just a little bit to close the gap between the guard and the tyre. Maybe an inch or two, don't want to go to low because it's my daily driver.