Both avenues are butt ugly.
Originally Posted by caslon
That's what happens when you buy a condo without ac in the first place.
Placing the unit on the deck eliminates all of the "problems" you are creating with the hole in the deck thing. A heavy duty rubber roof mat under the unit eliminates leaks caused by vibration.
Not having AC will drop your price. Exposed linesets and a hole in the deck will drop your price. The current real estate fiasco created by greedy banks could drop your price a whole bunch. A collapsing dollar will lower your price. Pick your evil.
Someone buying your condo with AC will realize that the retrofit has limited options. If it is done nicely, impact will be negligible to nonexistent.
I didn't see any patio furniture on your deck.
At least if your unit is on your deck the chance of vandalism is lessened.