[dice]

"CP x Black Krim"

This one probably has the potential to produce
offspring with the best flavor, but I don't see how
you improve on either CP or BK by crossing
them together. You probably end up with something
like Carbon or Paul Robeson or a slightly smaller
Cherokee Chocolate with subtly different flavor
(and you could just grow those instead).

"CP x Joya de Oaxaca"

This one has possibilities for unusual color and
shape, good flavor, etc. If Joya de Oaxaca is like
most cultivars from Mexico, it is probably quite
late maturing, and if you get offspring with a DTM
closer to CP that still taste great, that is an
improvement.

"CP x Watermelon Beefsteak
CP x Yellow Giant Belgium"

I don't know anything about these two. Mild
flavored? Productivity? Is it just size that makes
them interesting as potential parent strains?
Want to improve the flavor while still getting
big fruit? Feel free to experiment.

I would caution against making any judgements
based on the flavor of the F1 hybrid generation.
"Keep or toss" is an F2, F3, or F4 decision, when
you have a better idea of what the range of
flavors is going to be. If you have offspring that
is productive and robust and interesting-looking
but a little bland, you could cross the best F2
or F3 back to CP again to maybe improve the flavor.