The extant knowledge of the Mayflower is, of course, extremely scanty. At the moment I'm reading the most recent book on the subject of the Pilgrims and Plymouth: Mayflower, by Nathanial Philbrick. I highly recommend the book; it's both thoroughly researched and extremely well-written - a real page-turner. The title notwithstanding, Philbrick doesn't actually say much about the ship herself. (The transatlantic voyage is over by the end of chapter 3.) But the whole book is a solid, thought-provoking discussion of how Plymouth Colony was founded, and, especially, the evolving relationship between the English settlers and the Native Americans.
It seems to be generally accepted that there are two reliable pieces of information about the Mayflower: her burthen of 180 tons (meaning her hold would accommodate about 180 casks, or tuns, of wine) and the fact that she had topsails. (William Bradford's book, Of Plimoth Plantation, describes how, in mid-Atlantic a passenger named John Howland fell overboard and saved himself by grabbing the end of a "topsail halyard," which happened to be dragging in the water.) Professor Baker took all that into consideration when he designed the Mayflower II. By the standards of early-seventeenth-century (or late-sixteenth-century; Mr. Baker concluded she was probably pretty old by 1620) merchantmen she was actually on the big side. Mr. Philbrick suggests that she was about three times as large as the other ship the Pilgrims initially chartered, the Speedwell.
I've only been on board the Mayflower II once, and that was a very long time ago. I have a fairly clear recollection, though, that one of the costumed guides was standing by a carriage gun on the lower deck. When I expressed surprise at the sight of it, she explained that the researchers were fairly certain that the real ship had carried some sort of armament. Mr. Philbrick confirms that the Mayflower carried some guns of some sort - at least on the way over. In February of 1621, before the ship sailed back to England, the Pilgrims built a fort to defend themselves. The ship's captain, Christopher Jones, "supervised the transportation of the 'great guns' - close to half a dozen iron cannons that ranged between four and eight feet in length and weighed as much as half a ton." It's possible that some or all of those guns had been carried as cargo in the hold, but maybe some of them had served as the ship's armament.
If I remember correctly, the Airfix Mayflower kit includes some stubs of gun barrels to be plugged into holes in the hull. Both Revell kits have gunport lids molded in the closed position on the lower deck.
I haven't seen that Imai/Aoshima/AMT-Ertl Spanish Galleon kit in a long time, but on the basis of what I've seen of it I agree with EPinniger: it's about as close as can be expected, given the paucity of information, to a scale model of a real Spanish galleon from the Armada era.