I prefer XTOL replenished to develop film for better tonality and finer grain, but I have not tried it with B&W reversal. I would suspect that XTOL will provide finer grain than Dektol for slides. Dektol is a paper developer.
Indeed, paper developers are used in reversal processing because they are stronger than film developers which are too weak and give grey slides.
The developer recommended for reversal processing is Kodak D-19.