I agree with yohy, the Emirates lounge in BKK is really good and much better than the old QF lounge, let alone the third party lounge they direct you to now. Also find the food on EK J is better than QF J. Seat on the QF A330 is great, but I managed a good 5 hours sleep in the EK J 777 seat from BKK to SYD in May, might have had something to do with the 3 glasses of excellent white in the Emirates lounge before the flight, followed on by 1 champagne and then 3 glasses of white with dinner?
Having said that, I am always thrilled when I get to fly J, regardless of the carrier, so you will enjoy either flight. Relax and make the most of the service!