So you're saying you currently have full coverage with an actual cash value replacement policy and you are wanting to go to an agreed value? (I think "replacement cost" is more for "items" not vehicles, but I'm not certain.)
Agreed value "can" net you more in a total loss, if the vehicle has depreciated some since the value was set.
If that's what you're after, then that is the type of policy you would want.
Otherwise, simply keeping with a decent rated insurance company and KNOWING your policy, is the best defense against not recovering what you should in a total loss.
Success stories with "payout"? If you're just looking for someone to tell you how great their insurance company was, or how bad their settlement was, you'll get those stories.
But realize, you could swap the names of the 2 companies between the good and bad story and you'd find someone who'd have those experiences also.
Insurance companies are a FOR PROFIT business and also can be/are very unscrupulous. The only way to achieve what you want, which is the best sense of security for your item, is to KNOW your policy. Just like the rest of the world's industries, Ins Cos will take advantage of those that are ignorant to their rights and terms.
Hope this helps?