Selecting holdbacks

I was curious about what goes into consideration for selecting holdbacks, for those that do. Other than the obvious, such as gender and genetics, what about birth weight? Physical health? Perhaps a better way to phrase this is; forget about the morph and focus on physical/ fitness characteristics.

Why I ask, I have a pastave sulfer and super pastel mojave sulfur. Both female, but the super has what looks to be a slightly smaller jaw (not deformed), one little kink at the end of its tail (past caudal region, practically at the tip) and it weighs about 10g less than the pastave sulfur girl. Opinions would be greatly appreciated!

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Health, whether or not the animal is a great example of the mutation I want to hold back and whether it will fit in my future projects are the main factors for me, weight is not a determining factor.

In this case I would not hold back the animal, if it strive I would give it to someone that wanted a pet.

I can see the temptation in holding back the super, but (for me) I would have a hard time holding back a deformed animal for breeding purposes. The possibility of passing along the deformity would probably nix the animal as a hold back for me.
I have not bred any snakes yet, but I have a good deal of experience breeding horses, mice and rats. No matter how pretty the animal, if there is an imperfection that is possibly/most likely the result of genetics (vs an injury), it does not go back into my breeding program.
Use your own judgement, but keep in mind that you can always produce more of the supers with future breedings, hopefully without the issues this one has.

Same here. All depends on what the future plans are. I have a bunch of recessives so there will be a lot of "normal ;)" being held back for the next couple years.