Is round cage bad for birds? Round cage or rectangular cage?

I guess really it's a matter of personal taste. I prefer rectangular. Most cages tend to be kept on a piece of furnature which is against a wall. The cage also tends to be pushed to the rear. Birds do sometimes get frightened and like to perch at the rear of the cage where they know nothing can approach on their blind side.
If the cage is for parrot like a taller rather than longer cage is a better one. Budgies, cockatiels and lovebirds all like to climb up and down.