>>34588612What matters most is type match up and attack stat, followed by durability.
Dragonite is a great generalist for example, with base 263 attack and access to Dragon Tail/Outrage, it has some of the highest damage output, but no worthwhile type matchups
High CP is not indicative of DPS, Blissey has huge CP but hits as hard as a Horsea. Unfortunately the game has no transparency with attack stats, or stats in general.
Although if you have the raid numbers, you'll win regardless. Your own performance instead will count for how many premier balls you get.
Generally, the larger the raid group, the fewer rewards each participant gets due to how damage and team contributions work.
Lots of sites write up guides for what's a worthwhile attacker for specific raids. For example, right now Gyarados and Exeggutor are very popular for Groudon raids, but it also depends what moves the Groudon knows.