Roadtrek, Pleasureway and Winnebago all claim to be #1 - but that is probably in how they are parsing the numbers. Who knows for sure. Arguing about who is selling more of the 400 units a month is silly when total RV production is 36,000. All the volume is in trailers anyways.
But if you are talking to finance types or marketing types - it's all about the growth. The % growth is in B's. The money is in trailers. Growth moves stock prices and generates interest in your stock. I'm sure the Wall Streeter's are saying - "I see growth in B's is up 50% year over year. What are you doing in B's?", to which Winnebago will say "We're #1 in B's!"
I just thought it was interesting.
If you go to their history page there is more interesting numbers on total RV sales - 1978 was a year where 390,000 units sold and that was down 5.8% from the previous year. Sales have didn't beat this number until 2006. Sales tanked after that year - so you may expect good used deals on 2003-06 models since there are so many and maybe 2007-2010 models to hold their values a bit better since their numbers were way down.