It would be interesting to know WHICH BXUV-35 that you have.
Between the two you mentioned, my guess would be the Carter would give better fuel economy (I know, not the important criteria), and be somewhat smoother across the entire range of RPM.
As far as "seat of pants" performance, I am going way out on a limb, so dig out your saws

I think the Zenith would do a wee bit better in the 1/4 mile (maybe a tenth???), and the Carter would be a wee bit faster on the salt flats (maybe 1 MPH???).
In other words, between the two mentioned, use the one YOU like.
There are better Zeniths if one does some homework.
Jon.