The unit with the best price-to-performance ratio.

20 vs. 10 will be a complete stomp! It might be tough against the gray bears, but I think they'll crush everyone. One hit is enough for the phoenixes. They'll take out a good chunk right away. After the second hit, there won't be much left to fight with. And considering that 4 phoenixes will resurrect, it's game over.

It's clear that you don't have much experience in TC3. Without a chalice, the phoenixes probably won't take out even 2 archers at once, and 4 will die from the counterattack... then another 4, and there will be about 7 archers left against 12 birds, which is a completely different story. And the fact that 4 will resurrect is far from certain; the range is from 0 to 4... Although, phoenixes are indeed strong in terms of price/effectiveness, but bears are still the best overall, IMO.