Old text "Airplane Design" by Warner shows effect of three different leading edge radii for the NACA 0012 symmetrical section.

A knife-edged leading edge reduced peak lift coefficient from 1.4 to 1.03, but produced a very gentle stall. Minimum profile drag was reduced only by a percent or so, and was increased at lift coefficients over 0.2 - definitely a poor trade-off, apart from its friendly stall characteristics.

A very blunt leading edge with radius of about 5% of chord increased maximum lift coefficient to about 1.5, increased minimum profile drag by about 10%, and produced a far more abrupt stall.

The blunt section, with its higher lift and abrupt stall is good for maximum possible lift, clean snap-roll entry, at the cost of tendency to stall and snap-roll. This probably explains the popularity of the so-called ice cream cone sections used on Extras, Edges, and Sukois for all-out aerobatics. Just don't let your airspeed get too low during a landing approach.