Ken-
I know where you are coming from and let me add my $.02...
Italian
I have played Italian basses, and yes I agree that IN GENERAL they are THE all around best bass. I have played several different shapes, sizes, etc... they are all smooth, deep, resonant, and round sound that has the ability to either blend in a section or rise above it. If I was a top level professional bassist in a major orchestra- This would be the ultimate solo/orchestral instrument.
English
In my opinion, the ultimate orchestral instrument. It has just the right amount of spread combined with the smooth, refined, and beautiful sound of the Italian basses. Usually they have a little more "punch" than the Italian basses.
These basses are similar. In my opinion, due to the fact that most of these instruments were made on Italian patterns. I played a Fendt this weekend, Ron Sach's Violins in ATL, that is on the Maginni pattern. Very good sound-even after a year on the restoration table. Deep ribs, but very playable. Great wood and it will make someone an incredible orchestral instrument.
French
I played my master's recital on a Jaquet. It was one of the sweetest sounding basses I ever played. Unfortunately, I could barely reach the upper notes of the pieces. This bass was not the "typical" french bass. No Nasal here.
I usually feel that French basses are slower to respond. Thick tops take some "encouragement" to get the notes out on time, especially with the larger "cello-like" proportions.
The smaller basses can make great solo instruments and chamber basses if the tops aren't too thick. Those are usually better to the ear as well. Projecting- not nasal.
German
I own the exception to the rule here. Also, Klotz basses can not fall in this category. There are some great German basses, just most of them don't make it out of Germany. I think what most people associate with German is factory.
German factory basses are the workhorses. Great Jazz basses. Thick tops on some, but easy to play. Very accesible to players.
Yankee
The powerhouse bass. Most of these old Prescott's etc... are absolute organs. Spread for days, unfortunately not much focus. Dark, big, and power. Not the best basses to take an audition on, but once you get the gig the really fun ones to play. If dialed in, these basses can be the "new" english bass. Good for jazz, but better for orchestra, especially as they are getting older.
Those are the main schools to me. I have played Austrian/Czech/Tyrolean, but they are all over the road. Some more German, some more French, some just "out there" with qualities from the best schools. Hard to make a category out of these.
Just my experience. I would say I have played at least 10 of each of these schools, so take it for what it is worth.
IMHO,
Brian