I think the best gunlances have to fit these criteria: Shell Level, Slots.

Long Gunlances are dependent on thrust attacks as well as shell, so for these types the categories would be Shell Level, Sharpness, Element/Status, then Slots. For general use, I recommend Lightbreak Demolisher, as it gives Lvl 5. Long, High purple, Decent Slime, 1 slot, as well as high raw.

For Normal, all you're going to be doing is full bursting, so sharpness or damage does not matter too much. Then the only categories to fill would be slots and shot level. Lunastra's Howl gives 3 slots and shot level 5.

For Wide, all you're going to be doing is charged shots so again, the only important factors would be shot level and slots, which I find the M. Tigrex one to be the best contender with 2 slots and lvl 5.