I tend to agree with what's been said so far in this thread. The two Revell Mayflower kits are both excellent examples of the plastic kit manufacturer's art. And anybody who's confused by the differences between them is in excellent company.
The big difference between the two is that the larger one omits most of the rigging blocks that are included in the smaller one. (The smaller kit came first; the bigger one was part of Revell's "simplified," "build a legend in a weekend" series, which also included smaller versions of three big kits: the Constitution, Cutty Sark, and Thermopylae. There was one other kit in that series: the yacht America, which was a "new" design. If all that's confusing, don't worry; for any civilized purpose it doesn't make any difference.)
If you want to do a reasonably thorough job of rigging the bigger kit, Bluejacket (www.bluejacketinc.com) offers nice britannia metal cast blocks, deadeyes, etc. for the appropriate period. You may or may not want to replace the plastic deadeyes. If so, you'll have to decide between the "old style" (rather heart-shaped) and "new style" (round) ones. There are good arguments both ways.
I sure would like to get a look at the pantograph machine (or whatever they called it) that Revell used in those days to change from one scale to another. It must have been a miraculous piece of machinery. (I wonder how big the original versions of such items as the figures on the 1/110-scale Bounty were - and whatever happend to them.) Not all manufacturers of the Goode Olde Dayes used (or could afford) such equipment. I have it on good authority that the toolmakers at Airfix, for example, made their masters at the same size as the finished products. (I suspect that situation has changed recently, since Airfix has been getting its molds - or some of them - made abroad. Come to think of it, the computer has probably made the pantograph obsolete for such purposes.)
I do think Woodburner's observations about the kit's (or kits') accuracy need a little qualification. The Revell designers quite obviously worked from the plans of the Mayflower II, the replica built in 1956. She was designed by William Baker, a distinguished professor of naval architecture at MIT and one of the very best in the business at the time. As Woodburner pointed out, Mr. Baker made some concessions to practicality - most notably the addition of a foot of headroom to the below-decks spaces. Otherwise, his basic source of information was a set of old drawings by the English shipwright Matthew Baker (no relation), believed to have been made somewhere around the 1580s or 1590s. The "Matthew Baker Manuscript" includes several beautiful renderings of ships, but scarcely any clear indication of just what vessels they represent. The general scholarly consensus seems to be that they're pictures of English warships of the Armada period, but there's room for argument. (Some have gone so far as to suggest that they represent vessels of the Mediterranean. That strikes me as pretty far-fetched, but the bottom line is that there's plenty of room for argument about those drawings.)
In using those drawings as a basis for a reconstruction of the Mayflower, William Baker was - as he freely and openly stated - making a rather big leap of faith. His logic was that scarcely any other primary sources were available and he was right. The actual, documented evidence about the real Mayflower consists of two facts: she had a "burthen" of 100 tons (and measurements of tonnage in those days were so sloppy and inconsistent as to make that figure almost useless), and she had at least one topsail (which we know because a man was washed overboard and saved himself by grabbing the trailing end of a topsail halyard).
In recent years quite a few other scholars have weighed in on the question of the Mayflower II's accuracy. It's been suggested that she represents a vessel of 1590 better than one of 1620. It's been suggested that R.C. Anderson, another fine researcher who did a reconstruction of her, in the form of a model, back in the 1920s, was closer to the mark. (His Mayflower is considerably lower and squatter-looking than the Mayflower II.) Some writers have gotten pretty emotional about the subject; that, for better or worse, is how scholarship of the sixteenth and seventeenth centuries works. But the truth is that nobody really knows.
It does bother me a little that such reconstructions, due to publicity and the fact that so many people visit them, tend to get taken more seriously as pieces of research than they should be (or their designers intended them to be). During the past 50+ years the Mayflower II has, I'm afraid, come to be accepted by millions of people as the "official" version of what the Mayflower looked like. Neither William Baker nor anybody else with any sense would subscribe to that.
I'm reminded of the first set of "Jamestown Ships," the replicas of the Susan Constant, Godspeed, and Discovery that were built for the 1957, 350th anniversary of the Jamestown landings. The act passed by the Virginia State Legislature authorizing the funding for those ships specified that they had to "match" the mural depicting the three ships in the Virginia Statehouse, because that painting was the "official" rendition of the ships. (William Baker, incidentally, excoriated those three ships mercilessly. Their designer responded by offering to set up a race between his Susan Constant and the Mayflower II. So far as I know, Baker never responded. Good for him.) The current Jamestown Ships, fortunately, are much better; they were designed by Brian Lavery, who knows what he's doing - and wasn't given any restrictions.
If I were building a model of the Mayflower (heaven forbid) from scratch, my personal inclination would be to make it a bit beamier and squatter, with a less tapered stern, than the Mayflower II (or the Revell kits). But that's just my opinion - which certainly is no more qualified than plenty of other people's. The bottom line is that nobody really has any clear idea of what that old ship looked like. A well-built model built from either of the Revell kits will be a thing of beauty - and nobody will be able to pronounce it historically "right" or "wrong."