Color Burst floods your word with ink — coloured blooms spread outward through the letterforms, bleeding into each other until the whole word is saturated.
SMIL-driven blooms expand inside a mask clipped to the letterforms, so the ink spreads within the word rather than over it. feGaussianBlur and feMerge keep the boundaries between colours soft, which is what makes them look like they are bleeding together rather than stacked.
Color Burst is contained — the ink spreads inside the letterforms. Watercolor Bleed lets pigment escape the edges entirely, so the letters themselves go soft.