Personally prefer a floorplate, as you can usually fit a longer cartridge overall length compared to a magazine.
For those worried about a slow reload on a floorplate, you need to buy some Federal factory ammo as they all come with these plastic clips enclosed (usually white plastic now but used to be a helpful red/hunter orange).
You now have 10 extra rounds at hand, but you can add more if you want to feel like a cowboy on a goat mission
OK, part two of how to load a floorplate quick.
With the bolt closed (no rounds in chamber), flip the rifle over and pop open the floorplate. Hold the spring and follower together against the trapdoor and then load however many rounds into the magazine well.
You will need to remember which side the rifle feeds from when loading but apart from that, you can now pop the trapdoor back whilst still squeezing the spring and follower together.
Not quite as fast as a detachable magazine, but if you have a big scope mounted low to the reciever (and fat fingers) this is a much easier method compared to loading single rounds down from the top (especially on the short action Rem 700 which has a tiny ejection port).
Video showing what I am describing:
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