I reckon blades are a lot lighter than a real leg, which would give you an advantage once up to speed. Probably also better for energy recovery once you are up to speed. But as you say, worse for starts and probably much worse in corners, at a guess.
The reason I think it shouldn’t be allowed is that it’s a different sport, really. We have different classes of motorsport with different equippment – why not in athletics? In the same way that you don’t race, I dunno, Formula Ford with Touring cars, even if they were similar speed.
Although a separate class of mixed racing – that would be great to watch. Wheelchair vs able bodied. Or how about a ‘modified’ class of para athletes, with unlimited prosthetic tech allowed. Like telescopic legs, with a high pressure charge to fire you out of the blocks then they extend really long so you can bound along dead fast.