Glass electrodes perform best when stored in slightly acidic solutions, pH 4 buffer is a good choice. Reference electrodes perform best when stored in the same electrolyte that is immediately inside the reference junction, typically saturated KCl. Table salt, NaCl, can be used if KCl is not readily available. Distilled or deionized water should never be used as a storage solution unless you like buying new pH electrodes. When properly used neither design is inherently more accurate than the other.
Sealed electrodes are convenient and suitable for most applications.
Refillable electrodes allow the user to fill the reference cell with the solution of their choice, possibly improving the performance compared to a standard KCl electrolyte. The reference electrolyte in the refillable design can be recharged when it becomes depleted extending the electrodes life. It is a question of convenience vs versatility. A double junction reference has two chambers, the standard KCl-AgCl reference cell and a cell at the front of the electrode containing a screening electrolyte, typically KNO3. Many applications contain materials that will react with the silver or chloride in the primary reference cell either fouling the reference junction or poisoning the silver wire.