For good egg production, you want to go with Anconas, Campbells, Harlequins, Hookbills, Magpies, or Indian Runners (according to Holderread's website!)
I LOVE my Hookbills, and Harlequins are increasingly popular lately; in fact, if you like the look of a mallard, Harlequin drakes look very mallard-esque. They're very pretty birds - everyone here on BYC who has them is very happy with them. They were developed from a color mutation in a Campbell, and lay just as well as any Campbell can.
I don't have any Welsh Harlequins myself, but based on what you've said you're looking for, they'd be my vote for you!