Without knowing how and why your 54 fits and is beloved, it's going to be a crap shoot guessing which of the new frame sizes is going to work best. ETT, stack, reach, etc., are only useful insofar as you know how they relate to meeting your needs. While we can use the numbers to put ourselves in a position that works on one bike, it's not true that the same position will let us get the most out of another bike; we must understand the overall design and handling traits, and rider objectives.
In the end, it's not numbers that make a frame fit, it's design and use. To illustrate this point, consider these two bikes:
By the numbers, one or the other doesn't, or shouldn't, "fit," but they're both mine and they both are comfy and well suited to their intended uses.
Obviously, that's an extreme example, as they are very different bikes which perform very different duties. Even within the same category, though, compare the red Lemond above to this:
Again mine, and my favorite road bike. Again, by the numbers when compared to the Lemond, one of these shouldn't fit; 585ETT vs. 570ETT, for example.
So what's going on? Fit is mutable, and it takes a concert of numbers and insights to bring bike and rider into harmony.
More info about the bikes in question, and what the OP's goals are with the new frame, will help us address the question of which size to go with, or at least help bring to light some of the considerations germane to the decision.
If the OP is a 'gut felling' kind-of -guy, my gut says go with the 53.
Sorry for the long post, but if a pic is worth a thousand words, this was actually the short version!