I'm planning on getting an OD pedal, and have come across the Keeley moded TS-9 and the fulltone OCD.

Anyone have any opinions on the differences between them and the strengths and weaknesses?

Different beasts. There's loads of videos on youtube with decent OD comparisons, but it's always best to try them in real life.
I've got an OCD, and it's awesome if you want to add some sweet gain to your sound or boost it, too much gain can sound a tad muddy tho. The 2 settings are decent too, there's a noticable difference.
"Breathe, breathe in the air
Don't be afraid to care"

Fender Strat/Tokai LS80>few pedals>Orange Rocker 30