Paula was primarily a Sample chip, and to have 4 independent sample channels on a computer back in the mid 80's was pretty awesome (look at the prices of samplers like the Emulator, Fairlight and Synclavier at the time)... So it made sense to take full advantage of that if you were developing a game... Rich, full sounds rather than simple bleeps and bloops. IIRC Paula could modulate one channel with another, so you could set up a simple waveform (a very small looped sample) then mess around with it... Nothing really exciting. Sample playback was the exciting thing, but then all computers got that (at better quality), and it became the norm.
Personally I love the dirty sample sound of Paula, far more than the pure synth of SID... But it's much easier to make something which sounds a mess with Paula than with SID, so probably doesn't gain much traction with today's brain dead producers...
