To simplify the given expression, we first need to find a common denominator for the two fractions. In this case, the least common multiple of 4 and 6 is 12.
So, we can write:
\[\frac{x - 4}{4} - \frac{x - 3}{6} = \frac{3(x - 4)}{12} - \frac{2(x - 3)}{12}\]
Now, we can combine the two fractions by subtracting the numerators:
\[\frac{3(x - 4)}{12} - \frac{2(x - 3)}{12} = \frac{3x - 12 - 2x + 6}{12}\]
Simplifying the numerator, we get:
\[\frac{3x - 2x - 12 + 6}{12} = \frac{x - 6}{12}\]
Therefore, the simplified expression is \(\frac{x - 6}{12}\).
So, the answer is option (B).