the biggest difference is, the Flocculation and ester/phenol profiles of the two strains. I have used the Belgian ale yeast from omega, and it give a nice spicy and fruity notes when fermented at higher temps. I have not used the abbey ale yet.
Abbey Ale C --
This Abbey ale strain’s trappist origin is best coupled with a little monastic patience: a notably low flocculator, it is highly attenuative with a fruity profile and lightly perceptible spiciness, as well as often significant banana.
Belgian Ale A --
As one of the few highly flocculent Belgian ale strains, the thought-to-be Ardennes strain makes a great Belgian house. It is brewery friendly, crops easily and has a well rounded flavor profile that balances fruitiness and phenolics. Esters increase with upward temperatures.
if you are not a fan of the banana flavor then exchange it, but otherwise i would keep the current selection and see how it turns out, it will still give you a Belgian taste either way you go.