Very different boats
Cape Dory 27, Tartan 27 are older designs with full keels. They are quite heavy and need some breeze to get going. I prefer newer designs like the 28+/28. One thing you will notice is that the heavy full keel boats are less affected by having a bunch of cruising gear aboard since this weight is a smaller percentage of total weight, but the 28+/28, along with newer fin keel types, will be much quicker in lighter air, and be much better to windward (they point higher) than the older types.
All are good boats, but they will appeal to different types of sailors.
Enjoy,
S