@Deadhuntr: It seems from the screenshot that Naissos brings in more cash; it's closer to your territories so it's easier to defend; and the Makedonian army there looks weaker. I'd save Naissos if I had to choose. And if you decide to take this path, it's even better to destroy everything in Tylis so the Maks will have difficult times rebuilding everything; unless, of course, you are planning on reconquering it very soon.

Also, what's the diplomatic situation in that area? Is Makedonia at war with someone else? How are they faring in their other wars, if any? If they have some other problems, you could retreat, retrain, and prepare to strike in a more favorable moment, while expanding north or west and defending your home territories.

However, I think you can defeat both armies if you fight the battles well. Naissos should be easy; of course it depends on army composition. Tylis will be more difficult, but it looks that with some luck and superior tactics you can win. I would position the reinforcements near the besieging army and then sally out, so the Maks would be somewhat unprepared; unless you have lots of cavalry or some other kind of army which fares better on open ground.

I would train horse archers in Kallatis however. Think of them getting behind the phalanxes and unleashing a rain of arrows in their backs... while their fronts are threatened by your infantry