There's no one size fits all answer. When I tried using anything other than Jaeger/rogue or howitzer/rogue combinations because of army matchups, I often regretted it. So I'd say you're already considering the two most flexible options. I'm not in as competitive GBGs as you so I generally had enough time to have the option of surrendering to get more favorable terrain or attacking a different sector to get a new defending army, which gave me more flexibility. And even the choice of full auto battle vs making one move followed by auto might change the best choice.
In your circumstances, I'd stick to Jaeger if I couldn't take time to choose but if you run up against howitzers or few trees on the map you could be out of luck. In case it matters, I'd add that in battles I won I was more likely to lose howitzers than Jaegers and I would have had to store a building and build a howitzer factory to restock if I hadn't been ready to move to PE