I suggest that you look at the current Herald vs F27 thread in Aviation History and Nostalgia subforum:
http://www.pprune.org/aviation-histo...erald-f27.html
Comments there indicate that the Herald was a rather slow dog compared with the F27. For example "the F27 was about 20 to 30 knots faster than the Herald for the same fuel flow". But "The Herald had better short field performance and higher cross wind limits and hence was very popular with Channel Island operators."