Never, never, never /sell melonslice: they are worth 0.10 each, while a melon block (which is made out of 9 slices) is worth 2.00. It's more than double and all you have to do is /condense all, or just do it by hand if you don't have that command. That's the 2nd most wrong thing to do on ECC, after /sell nstar. P.S: and if you have a silk tool, any tool except axe, use that one rather than anything that would drop slices instead.
Looting doesn't affect it, but like @Expipiplusone said, better to just make it a full melon block, they are $2 each
As Lego said: loot doesn't affect, but fortune does: http://minecraft.gamepedia.com/Enchanting#Fortune However with fortune the max number of slices per block you would get (from a melon) is capped at 9, therefore the average number will be necessarily less than that (probably around 6 slices/block with fortune3, vs 5 slices/block without it, not such a big difference). TL;DR: silk is still better than fortune (with our current prices).
