Bahco625-ROUND Farbschaberklinge, Klinge 625-ROUND-Rund, silber

What diameter is the round part of the blade?

When blade bahco h865-1 2-1/2-inch wavy works better than bahco 451 2-1/2-inch straight edge?

In the picture it's shown with the thinner rounded edge out; if you turn it, does the wider rounded edge stick out enough to use?

What's the advantage of the wavy blade versus the straight blade? When is the wavy blade better?