What is the difference between open and closed jawari?

On a sitar, open (khula) jawari gives a brighter, louder and buzzier tone. Closed (band) jawari gives a warmer, plainer tone with more sustain, and round (ghol) jawari sits between them. Ravi Shankar's sitar is the usual open example; Nikhil Banerjee's and Vilayat Khan's are cited as closed. Open jawari also wears faster and needs re-filing sooner.