I recommend starting with color.

Best advice I ever got from a painter-friend was to simply limit your choices to the Benjamin Moore historical colors. This way you don't have to look through 1200 colors, and all of them are great. (and if you prefer another brand, just have them color match it.)

Benjamin Moore has a fantastic website. You can literally upload a photo of your actual rooms, and then "paint" them and see how they look. This is very helpful, especially to see how colors look next to each other.

Lastly, I think that your styles have more in common than some do. Both would incorporate horses, weaponry, nature, and hand-made items. So try to find these aspects in each others decor items and try to incorporate them in interesting, but simple ways. Too much is just too much.
Personally, I would avoid the "his and hers" literally, because it may become too "theme-y".