George,
You're sure to get many opinions. I have a 4.2M Explorer and it has had 2 motors on it over time - a 30HP Merc Lite and currently a 40HP Yammie 4S. I put a suitable Permatrim foil on each motor with very impressive results.
I haven't tried any other type of foil so my experience is limited. All I can say is that I have absolutely no reason to try any other type.
BTW, the reasons I put the foil on each motor were:
to improve planing performance
to reduce cavitation during turns
to improve trim of the boat