When I discussed this topic with Boskalis, they told me the Vasco da Gama (Belgian flag - perhaps now Luxemburg flag?) was the biggest and the recent modification of WD Fairway (Dutch flag) would be more or less identical.
So how do we compare these two?
By DWT or Hopper capacity as the latter seems to be the norm.
Jan de Nul owns the Vasco and Boskalis the WD F.
Vasco da Gama WD Fairway
Built Thyssen Emden 2000 Verolme Heusden/Sembawang
length in metres 201 m. 232.35 m.
breadth 36.2 m. 32
draft loaded 14.6 m. 13.68
DWT 60,000 59,798
Hopper capacity 33,000 cub.m. 35,508
Kw Engine Power 37,060 27,550
Going by the hopper capacity, then it would be the WD Fairway which is the largest, so my initial posting was perhaps not right.
Prior to the conversion the WD Fairway had a hopper capacity of around 23,000.