Not sure of the st angle on the small Terry's but they have a 700c back wheel and a 24c front wheel. It means carrying 2 different sized tubes and stocking 2 different sized tires. At least with 650's you only need to worry about having 1 size with you.

BTW, I saw a custom Luna last week at Ride the Rockies, it was very small and it was a beautiful little bike.