A quick forum search found nothing for SAGA Dark Age. I couldn't even find it on boardgamegeek.com or on rpggeek.com.
From what you describe, and what I saw on the publisher's website, I think either program would be well suited, but BGE is the more economical option.
Check out the features that will be coming to BGE v1.8, shown in this video
, paying particular attention to the unit grouping section.