Does U-235's Higher Likelihood of Fission Make It More Useful Than U-238?

[textbooks]

U-235 is most suitable for bombardment by slow neutrons 'cause it becomes U-236,providing for a more balanced nucleus. So if the electron shells are arranged something like 2,4,8,16,32,18,8,2 the atomic number only changes, in this case, because of an additional neutron. Is this element in a more harmonic state now, is this why it is useful? and U-238; would the same be true simply because it has an even atomic number after bombardment? "Anddoes U-238 have the same electron numbers in their respective shells?
L8R

 

[Astronuc]

Please show some work and attempt to answer one's questions.

What is common among isotopes of any element?

U-235 is one of the fissile or fissionable isotopes, whereas U-238 is considered fertile.