I understand what you're saying, however I don't agree that most of the advantage is for the advanced player on the Bb side. With the partials further apart, it would make it less "slippery" for a beginning student. The frustration factor is a real one, though I agree that from a pure sense it is best to go with the F horn.
As one who has taught both middle school and high school for 25 years, I can assure you that the surest way to run off beginners is to give them a horn (Bb or F) as their first instrument. They will be terribly confused and frustrated.
All of the concern about starting on a Bb or F horn can be solved by making sure that the student's first instrument is not a horn. Have them play flute or clarinet for a year. They will develop as horn players faster and without the drop out rate of those who start on horn.
Richard Smith R.G.Smith Music Engraving & Publishing <http://rgsmithmusic.com/>rgsmithmusic.<http://rgsmithmusic.com/>com [EMAIL PROTECTED] _______________________________________________ post: [EMAIL PROTECTED] set your options at http://music.memphis.edu/mailman/options/horn/archive%40jab.org