The right pair of mudguards depend on the usage of the bike.
If it will be used in the snow and/or off road then I'd go for a set of MTB style guards like
these, as snow/mud/other won't get caught up in them - Although they offer less protection from the frame being sprayed in mud/water. I have the rear guard that I linked and it has a rock solid mounting, but the actual guard is a bit flexible to prevent branches etc being caught in it. Over all a great design.
If the bike won't be subject to mud/snow which could get caught in tighter fitting guards, then some SKS commuter style would be better as they provide better over all protection from spray, to both you and your bike.