I personally like the Nieuports ( with the exception of the 28) I have a replica of a RFC modified Nie16.
Albert Ball ( and many other aces) prefered the light and agile Nieuports over other aeroplanes. Albert Ball had a Nieuport even when he had a SE5. He thought the SE5 a great disappointment. I will soon be building a full scale NIE23 myself. I think if you are asking what is the best WWI aeroplane you must pick a year and time period. The BEST changed every few months. I don't like late war aeroplanes as they might be too good ( and expensive to make because of the High Horse power engines.) I prefer mid war aeroplanes myself although I think that early war aeroplanes make a great model for ultralight aircraft. I have a friend that sells kits for a great looking scale Fokker EIII. Fokker DVII are HUGE aeroplanes to build anyway. I like the smaller aeroplanes like the Nieuports , Sopwith Pup, Hanriot HD1.
Cher'o,
Lt. Dwight Rudder, RFC
Great War Aeroplanes Asso.
Nieuport builder
St. Louis Escadrille