I perfer Bodom's song writing style personally. Each of their songs has a standout thing. Whether that be a solo, melody, duel solo, or lyrics. Theres always something in Bodom's music that stands out.
Plus, Bodom wrote my favourite album of all time, Hatebreeder. As great as Kalmah are. I doubt they will be able to write such a masterpiece as Hatebreeder. But you never know.
Kalmah are probably in the top 5 of my all time favourite bands though.
To compose songs like Hades, Heros to Us, Moon Of My Nights, Alteration, Withering Away etc. The talent in the band is obviously some of the best in the world today.