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The bashguard is fine if you intend to use the bike for commuting wearing normal pants. The only negative thing about it is that it makes it harder to reach the chainrings for cleaning.
A rear derailleur guard is somewhat usefull for a MTB that's actually used as a MTB. However damage is usually from below due to rocks rather than on the side.
Fenders are useful if you intend to use the bike for commuting and would rather reach your workplace clean if you can't shower/have a change of clothes there.