The difference between II, III, and X models(be it on a PMA, PSA, PCH or PL) is in the appearance or wood selection. II stands for 'graybark', III stands for 'autumn oak', V is for 'ironwood', and X is for exotic woods. I talked with Roger at BW about performance differences between the different woods and he said they are very, very close.
The PMA has an 18 inch riser, 5 inch sight window, and depending on what limbs you get, can make a 58, 60, 62 or 64 inch bow.
The PSA has a 16 inch riser 4 inch sight window, and, depending on limb length can make a 56, 58, 60, or 62 inch bow.
The PCH has a 14 inch riser, 3 inch sight window, and depending on limb length can make a 54, 56, 58, or 60 inch bow.
As for a comparison from shooting different models, I can't help you there. My only recurve is a PMA II.
If I wanted a 60" bow I would look at the PCH first because it would give you a longer working limb, but the PSA would give you the longest working limb in a 62" bow.
If you call BW they would be glad to answer your questions. Their customer service is the best, and there is the "test drive" program if you want to try out a few different models.
You won't go wrong with a Widow, no matter what model you choose!