It's a long story but I have a great respect for ICG. I don't use them but own many classic coins that they graded. They always have a table at the January Fun Show. Friendly folks that give free opinions and love to talk coins and teach what they see in a coin. You won't get that at the PCGS or NGC table. I take in a nice group of coins at Fun each year to have graded. This year It's going to NGC. PCGS customer service did not care if I was a member any longer.
I don't use ICG. Only have once. But I really like them and they are an asset to have at coin shows with their free assessments of authenticity of coins, etc. But these days I'm all in with NGC. Their customer service is solid and their speed of service is fantastic. Love their holders, too. And, for what it's worth... more of my NGC slabs have been CACing than PCGS lately. Like 50% more.
Funny, I get EXACTLY that at NGC's table. But then again, I don't take mine there when it's the busiest part of the show, and I usually have all my coins ready to go, with a fully filled out and accurate submission form. When you go when the table is empty, they WILL just rap about your coins, if that's your thing