I'm assume that we have 15K troops for Hi Shin and Kyoukai Unit and 30K for Rigan Army like how they initially started? Then.....
I think Hi Shin Unit will obviously win this but it won't be an easy fight. Kisui is a underrated general, he has potential of Great General or Three Great Heavens (can't remember which one) and seems to have a fairly caliber of Instinct based on Keisha's and Kisui's own words. But Shin's Instinct right now is on par with that of Duke Hyou. Strategy wise, Ten is certainly a better strategist than Ryuutou. Don't really care much for Batei so he could get mid diffed by Kyoukai. But the disadvantages for HSU is that the morale of Kisui Army will be higher and pretty sure it stated that HSU is not really great at siege warfare if I remember correctly. But HSU would still win with let's say, 2 - 3K causalities.