Totally subjective obviously but general consensus and my personal opinion is that GF CL food is 'better' overall than Poly CL. When I say better, I mean more variety, fresher ingredients, more proteins & veggies, less basic fried food. This applies to both adult food and items kids might eat - GF just has more variety. I have not stayed SL (only RPC) but basing my comments on the understanding the food is the same in both. Note it is still somewhat mass produced Disney food, so keep that in mind. It's just more artfully prepared at GF.
Poly CL food gets the "just OK" vote in my book. Some nights are better than others. They've recently enhanced the afternoon snacks slightly. Note Poly CL DOES have hard boiled eggs at breakfast, this was added a year or so ago (THANK GOODNESS!).
But, for what Poly CL lacks in food, it makes up for in atmosphere and physical setting. It's arguably the best CL lounge on property from a physical setting/view perspective. I can't vouch for all of the CL's but from what I've tried, this is my favorite place to be. Here's an early morning shot:
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Daytime view from the third floor looking down on the second floor. The third floor offers a small seating area (that's almost never used that much) and a restroom! The restroom comes in very handy on arrival days if your room isn't ready and also departure days if you're hanging around after checkout.
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Here's looking back to where they serve the food. It's not on in the pic but there's a TV and kids seating there to the left. A stairwell on the right connects all three floors.
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Here's an example of evening Poly CL appetizers this past July.
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Why does every photo of mine have a Longboard in it?
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Usually three desserts per night plus cookies not shown. Pretty standard Disney dessert party stuff usually. I recall the desserts at GF being more impressive.
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Let us know what you decide!