It depends on the time and space you have for the dog..
Danes are wonderful proctective dogs, who love you till the day they die, but they need space, and you might want to put money away, they can have bad health problems.
A golden is healthier and less protective but needs a little more grooming. They need less room but just as much exercise. they are very good for the family and kids. they have problems when they get old, and will need special attention then, but other then that they are good dogs.
I think you have alot to think about, and it should take sometime. I also think you should adopt from a resuce or a shelter instead of paying alot of money for a something you can get cheaper and needs a second chance.
Both dogs are great, personally being the big dog lover I am, I would say Great Dane, but like I said, you need space and money. Also with a Great Dane you need firmer training then with a Golden.