Some general ramblings on the subject.

Generally speaking, stems are cheaper than handlebars. I assume that you have a bike that requires a 1" threaded stem (Nitto Pearl?). A quill stem and B123AAs will make a DEEEEEP drop that may not be comfortable. Looks nice, but not comfy. If you switch to a quill to threadless adapter then your stem + handlebar combinations are GREATLY increased. Yes, it may not look pretty, but no one will be able to catch you to tell you about it, hahaha.

If you are really considering racing, I'd suggest trying bars in your hands before you buy them. Bars come in 1cm increments for a reason.

But, to answer your question, people generally go for the same or slightly more narrow bars on the track.

Here is a teammate's bike which uses a stem adapter:

Chrome Paris Sport-1.jpg

These are B125s (more shallow that B123s and B123AAs). Imagine where the B123 bars will put her hands...now imagine if she had a downward facing quill stem.

In short, if you intend to race, stop in for a bike fitting. You'll save money that way. By the way, 80-90% of bars used in local track races are road bars.