a/c for lung room?

my lung room is 144 sq ft. and i have a 4x8 and a 4x4 tent in it. my question is should i use a 5000btu or 10000btu window unit i have both and was thinking about using the larger unit but read that an oversized window unit would not work as well what would you do?

you must calculate the heat charge for all the apparels in the room
(lights, fan, ballasts etc)
multiply the total wattage by 3.4 to get the btu

hot climate (during summer) will also influence the heat charge to dissipate