For my ridng use, I consider mudguards to be a complete nuisance and inconvenience.
I've broken countless mudguards over the years, and the Topeak Defender being the worst of the lot, with two breaking in a row. Ridng off road, sooner or later you are going to fall off riding off road, and in the case of the afore mentioned it will snap.
Other inconveniences include getting snagged up on branches and undergrowth whilst riding tight terrain, being right in the way when the time comes to move/carry the bike over an obstacle/fence, and in many cases the mudguards fit too close to the seat stays, and just cause problems in relation to build up of mud and leaves.
I've lost count of the amount of mtb events that I have taken part in, where people using mudguards have either had them ripped from the bike, or just removed and discarded them in the hedge.
I probably ride about 3,500 miles a year off road, riding three evenings/nights per week, and at least one day over the weekend, in all weather conditions, and my conclusion is that the only place that needs protecting from mud is the face. A front Rapidracer Neoguard is all that is required for that.
Each to their own though.
Typical winter riding conditions where using a mudguard has caused me hassle.