In reply to Robbie11:
I own several crampons with both types of fitting.
I think the plastic bail with a strap if it fits your boots well is the most secure type of fitting and is faster to put on and take off than a metal toe bail bar.
The welts on boots that the metal bail bar fit in to do have a tendency to wear down and the bail bars tend to bend and also give less front point protrusion as soles wear down. Also their is nearly always some play in the bar crampon interface.
A well fitted C2 (plastic) style fitting the crampon should stay on the boot just from the metal posts on the crampon without any of the straps being down up. This leads to a bombproof fitting with almost no play in it.
Further point to look our for when crampon fitting - The sole of the boot and crampon should fit closely together (without gaps between the frame and the boot). The bottom points should cover the sole well and no be too much to the inside or outside. The front points should be in line with your kick direction and not off to the side with good front point protrusion.
I find when a C2 crampon is fitted like this its the best fitting out there, super solid and just will not fall off. I've never had either type fall off in the field however I have seen C3 crampons fall off a few times even on routes!
For me the main advantage of a metal bail bar is it looks more 'pro'
