Answer
They will charge at different rates. The capacitors charge more quickly in the first circuit, with the two capacitors in series.
Work Step by Step
In Figure Q26.18a, the two capacitors in series can be replaced by an equivalent capacitance of $\frac{C}{2}$.
In Figure Q26.18b, the two capacitors in parallel can be replaced by an equivalent capacitance of $2C$.
The time constant $RC$ is smaller for the first circuit, which means that the capacitor charge more quickly approaches its final value (page 864). The capacitors charge more quickly in the first circuit, with the two capacitors in series.