well, i buy Field of Glory and play it a littke, can say that for me is more game than HPS games, yes, is an easy game to play but not easy to win against a human. You can have infinite scens (editor is great) and the expansion system is interesting, i see the original table game and are books covering medieval wars for example and dont talk about modding, someguys are working in a napoleonic mod... yea, HPS games are more "realistic" (i dont find Field of Glory unrealistic only find that have some... call it bugs that do the experience a little psss sometimes and have some features missing) but they have 2 years and Field of Glory only have 3 months with 2 patchs in this time.
If you want a easy game with a great number of units with a good mod potencial and great editor Field of Glory is your choice for ancient wars and with a little luck you can play games to the musket and pike era