From my understanding, you qualify for Dubai Connect if your layover is 6 hours or more when flying J or F; so I would check this again to see if you do qualify or not.
If you don't qualify, I would suggest the best thing is to pay the extra money and spend time in the F lounge.
Not if a shorter connection on the same day in the same cabin was available (even if more expensive or a later departure for first flight to cause it).