In my experience a 2 blade flies much truer.Only broadhead i use now are Bear Razorheads in 145 gr.,they are an older head but have stood the test of time and work very well.There's lots of different heads out there,you just have to decide what works best with your set up.
Have to agree with Rich about the Bear razorheads, little hard to come by but sharpened them up with a file and finished with a leather strop, man they get scary sharp and had a heck of a bloodtrail this fall, just wish they were still being made.
I shot my first animal, a groundhog, with an old bear fiberglass arrow tipped with a razorhead that I got from my grandfather. When I got interested in trad I bought a 50# recurve off ebay. I got some arrows that flew well but those bear arrows were terrible. Of course I knew nothing about spine. My arrows curved counter clock-wise in the air and it was a miracle that I even hit the g-hog. It actually completely turned around and the arrow went right through the boiler room.
For 2 blade heads ..Zwickey's Are very good heads as well as magnus. or Ace broadheads. A KME broadhead sharpening kit makes getting 2 blade heads hair shaving sharp easy.
As far as the "best" broadhead for a recurve?...truthfully it's a matter of preference...Iv'e used them all and they all work. Everyone seems to have their own set of pro's and con's...But truth is...shaving sharp broadheads and shot placement are far more important than broadhead type.