Scott:
They look surprisingly good with excellent detailing and a wide variety of poses. I thought long and hard about scale when I first began my Waterloo diorama (as I am sure you did also). If you plan to "do it big," room and resources make 54mm a very challenging and costly project. The factors that ultimately helped me to decide were these:
1) My old eyes have enough trouble focusing to paint 54mm figures, let alone anything smaller.
2) 28mm figures always seem to have odd proportions. If you ask me, they usually look like Oompa-Loompahs.
3) 54mm dioramas (particularly viewed live) have a much greater visual impact, especially on a large scale.
For years I have been planning to see the Siborne Waterloo model at the National War Museum, London. I finally went to see it in November, and I must say, it is a very impressive model. But...a couple of things to point out: the model is in 6mm scale and the figures are barely recognizable (whole regiments of just a patch of shape and color from any distance). Also, Siborne represented every two troopers with one figure, so the figures on the diorama are really one half the actual number. Finally, very few Prussian troops.
It is true that doing a 28mm diorama will permit you much more room and cost far less to produce, and if you are ok with plastics, you also have a pretty wide range of options. With figures such as these, you may be able to avoid the Oompa-Loompah factor.
It's not that I am a purest, but I am committed to 54-60mm and almost exclusively metal (with the exception of some wagons, carriages, and of course, buildings)...I just like the weight, the feel, and the relative durability.
For me the deciding factor, though, is the availability of fantastic quality 54-60mm Napoleonic "collector figures" that really bring a diorama to life. A also like mass-scale, but I think the quality of the pieces you use has the greatest dramatic effect to the display...and of course your imagination and creative ability to deploy them.
I'd be interested to hear what you decide. If you have a decent number of quality 54mm figures to sell, you may be able to finance the entire 28mm campaign!
I'd love to have the space that I have for a 28mm diorama, but I could never start over again!
Best wishes in your project.