The pronounciation will vary from region to region, person to person. Ch became ts in standardized Tagalog because the orthography was "Tagalized" after WW2. They tried to follow the "orthography" of the baybayin so they rid of Tagalog of Spanish "loan letters". This is the reason why if you look at the American-era Philippine coins, you'll see "Filipinas". After the war, it became "Pilipinas"
But pronounciation wise, you'll also hear it as cuchillo or kutchilyo. Some languages in the Philippines have the "ch" sound like Ibaloi and many Filipinos can pronounce the "ch" sound. I pronounce it as kut-chil-yo because that's what I grew up with.
Tagalog used to follow Spanish orthography.
Whether it's kootseelyo or kutchilyo, it doesn't matter. Just make sure you don't say malaki ang súso when you mean malaki ang susó. Lol
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