Masthead Sheaves--re-cut old aluminum or buy new delrin?

[JohnV]

The 3 pairs of original bronze-bushed aluminum masthead sheaves on my '79 Alajuela 33 cruiser were grooved for wire and rope.
I want all 7/16" rope for simplicity's sake. So, I need rope grooves. Machining the 6 old ones will still leave me with about 3 1/8" diameters (7.1 times rope dia.), and aluminum obviously has greater strength.
Six new Delrin sheaves would be lighter, a little bigger at 3.5" diameters (8 times rope dia.) probably cost not much more than the machine work, and entail less chasing around.
Is there a significant reason to go one way or the other--old aluminum or new Delrin?
Or is it a coin-toss? (painful metaphor, huh.?)
Thanks for your thoughts.
John V.