Actually, the slightly wavy/curly fur is permissible in the show ring. There's alot of other things to look for besides fur--structure, gait, angulation, topline, etc. etc. Also in the American shows because handlers are always used, the more popular handlers usually win, regardless of whether or not the dog they were handling is the best in the ring (alot of political stuff going on here).
The problem with the colours is that the Blenheims are the easiest to show. They are much more numerous than the other colours, and they usually have better heads, etc. because breeders have focused on Blens for such a long time--it is just easier to come across a Blen of outstanding quality than in the other colours. Tricolours are the HARDEST to breed because the standard calls for a blaze and a broken up coat. The particolour gene (in Blenheims and Tris) is expressed more strongly in Blenheims, which is why you see most Blenheims have broken up coats and wide blazes where as Tricolours are often blazeless or have very black, blanket coats. To come across a really beautifully marked tricolour with outstanding head/structure is a rare treat indeed. (Google "Rathbrist Rhydian".. he is currently my favourite tri because he is just absolutely STUNNING. He's got a beautifully broken up coat, nice blaze, and an outstanding head. He has won multiple BIS in the UK)
This is why there are fewer tricolours in the ring. As for the whole colours (black & tan and ruby), they are less numerous, and it is harder to come across one with great coat, structure, heads, etc. etc. Also it is harder to show them in the ring because they are less "showy" colours. The dark colours sometimes makes it hard to see their expression (soft expression is one of the most important things in Cavaliers).
Oh, and I don't get the Pekes either... I always think they look like alien babies, lol.
Cadence the tricolour Papillon (DOB: July 2nd, 2009) & Lyra the blenheim Cavalier (DOB: April 28th, 2011)