SpartaDOS: Subdirs and max.126 files
SpartaDOS X & BeweDOS: subdirs max +/- 1400 files
Mydos: Subdirs +/- 120 files.
The best DOS for big directory's should be BeweDOS runs all DOS 2.x software and is SpartaDOS compatible, it even runs Turbobasic and uses no RAM under the OS like SpartaDOS does.