4 things that make a toilet easier to clean:
Super gloss porcelain glaze. Some manufacturers use brand names: Duravit's Wondergliss and Toto's Sanagloss.
One piece construction: Dust and mold can't accumulate in the seam.
Skirted sides and vase-shaped design eliminate surfaces that collect dust.
Insulated water tank: Eliminates condensation on the tank surface during hot weather, inhibiting mold growth.
Sorry about the picture quality.
We have 2 Duravit Starck 2 toilets upstairs installed 2008 and a Eago TB353 in the downstairs powder room installed last spring. All 3 have all the above features and work great. The Duravit's bolts were visible, so I applied a round piece of thickish glossy white vinyl over these openings. Voila, problem solved. The vinyl looks just like the removable plastic covers some toilets have, essentially invisible.
Additionally, the newest of the three, the Eago has a dual flushing system that is the quietest (and shortest flush/refill) I've ever had the pleasure of barely hearing. No double flushes needed, ever. After 9 months use, we've never had to use a plunger either, and the Super Gloss Glaze stays super shiny and clean for a very long time.
Good luck with your search!
Q