I have limited experience, but I will weigh in anyway.
The OD on my Marshall mg-10 sounded ok (all things considered)
The OD on my current amp, a Drive CD200r is really weak and sounds awful.
My fave is my little Livingstone Heave Metal pedal which my aunt bought for me because I hinted that I wanted a reverb pedal (she's 78 years old, so they are all the same to her). Really sweet attack on it, it makes me just wanna shred, nice sound, and when I take the gain all the way down and the tone all the way up (or maybe the other way around, I can never remember which) it makes a sound like I am playing out of a crummy AM radio.
All for $30 from a supermarket.
I want to get the chorus pedal they have if I could ever find one...