I need to know which platform would be the cheapest, most creative (in terms of flexibility and audience support). I want to introduce a hobby platform. Thus far, I'm toggling between Arduino and PIC. I need to take the cost of the board to the bare minimum possible. My audience are novices. It shouldn't be too complicated, yet it should be flexible enough to let us create as many projects as possible. This means compatibility with external sensors should be good.
I am in the same position, and I chose the Arduino. There's a nice software development platform, lots of instructional materials, and numerous vendors to choose from.
There's even a really nice open-source "getting started" tutorial.
Check out this beginner's kit. I bet you can adapt this with the clones mentioned by RedGrittyBrick and have a very nice, low-cost setup. Let us know what you end up doing!
Sparkfun Inventors Kit http://www.sparkfun.com/products/10173
You are not really comparing like with like. PIC is a family of microcontrollers. Arduino is a prototyping platform.
The Arduino platform is popular and easy for novice hobbyists to get started with.
There is probably an equivalent PIC prototyping platform (or several) but, so far as I know, there isn't one with the same sort of appeal or success in the novice/hobbyist marketplace
Low cost Arduino clones
While the Arduino has a nice community, I think the PICs from Microchip offer a lot more options and flexibility. With the free Microchip compiler and $25 to get started with a Microstick it's pretty low cost too.