It's a valid question, though one that's been asked before (albeit less frequently than other newbie questions).

In my experience, it's not as simple as smoking a longer cigar for a longer smoking experience with the same flavor profile. You may find that the flavors you'd noticed in the robusto vitola aren't as prevalent in the churchill variety. You may find that you prefer different vitolas of cigar blends, simply because of the vitola that's offered. For example, you may find that you like Cohiba robustos, but not VR robustos.

There's another thread somewhere that talks about all of this.