Hi there Dan,
Armeos and Masouri are basically one and the same. Technically they are two separate villages, BUT in practice Armeos is a short extension of Masouri to the north. As neither is a giant village, you can walk to most main crags from both Armeos and Masouri. To give you an idea, the length of Masouri can be walked in about 10-15 minutes (add another 2-3 minutes to walk through Armeos). A factor which may or may not influence your decision is that Masouri features more amenities (i.e. restaurants, mini markets and more hotels / rental units) whereas Armeos consists only of houses, a couple of small hotels and some rentals; but, again, since this is an overall small area you can just walk from one end of the village to the other in no time.
If you have the new guidebook go to page 193, bottom photo. See where the path to the crags begins? That’s where Masouri ends and Armeos starts – you can’t tell them apart, and they are both near the cliffs.
I hope I didn’t add to your confusion!
Katie