Great question Andrew! Picks make a big difference in tone. Soft to mediium guages are better for strumming chords and thicker picks produce a warmer tone and better for single note playing.
I use "Gravity" picks (model 'Striker big mini') for electric guitar. They are heavy and thick picks with smooth edges which I like.
For acoustic guitar playing I use "Dava" picks because they have a rubber grip (so it doesn't spin in my finger grip) and they are a little flexible, which is good for acoustic chord strumming. I hope this helps.
Keep those fingers flying!!
-Dave