It doesn't matter if it is a 744 or a Dash-8 doing 180kts. They are both going to make the same turn radius.
In my personal experience, this doesn't always seem like it to me. I have found the DH8's to be quite nimble in the TMA, but have experienced the big-heavies make much wider turns at the same ground speed. Maybe angle of bank is an affecting factor? A DH8 will get it's wing down a lot quicker than the big uns...
Cheers
URC