I have had both, currently still have Pinball Pool.

Both are very fun machines, both lots of drop targets, both allow you to collect maxed bonus by hitting a saucer. The shots in Count-Down are somewhat more varied due to 4 flippers and spread out banks, but both are symmetrical layouts. pinball pool allows you to shoot directly at the saucers to collect bonus as well as increase bonusX. Count-Down you can't really shoot directly into the saucer at the top, it's more random and nudging to collect the bonus when it's lit. Also can't really directly shoot the extra ball and special collect lanes on count-down, while pinball pool collects extra ball by hitting the captive ball, which often leads to a stdm drain.

I would still have both except I sold my house in town and moved to my cabin and needed to downsize. The selection of which to sell came down to Pinball Pool was already at the cabin while Count-Down was at the house in town so I had less moving of machines to do. Count-Down will generally cost you more to buy than Pinball Pool, more well known/popular. Can't go wrong with either in my opinion.

edit: nice collection you have. either of these goes well with Joker Poker for variety, non-symmetrical vs symmetrical.

I added chimes to both of mine, love em. was easy, no extra wires at all.

Here is how to do: https://www.pinwiki.com/wiki/index.php?title=Gottlieb_System_1#Converting_From_a_Tone_Board_to_Chimes