Actually the DC58 is better than the DC31, because the DC58 has a screen for the shroud, which is like a sieve material so the filter won't get as dirty. Hair can't get to the pre filter and grit probably cant either, my DC41 filter never gets washed and was still spotless 7 months later and it hhas a metal screen
The DC31 has large holes which makes the filter more likely to get dirty and the cyclone more dirty, also more blockages are likely because larger things can pass through, especially when it's a handheld and it gets angled for different awkward areas, the dirt goes towards the shroud.
I would much rather have that get dirty than having to wash the filter all the time