if you are starting now, I would chose something that has more legs in terms of its expected life. I would focus on the 32-bit market if you have to choose one. Any of the arm chips, particularly the cortex-mx chips, would fit the bill. the lower-end ones come with an integrated debugger (lpcxpresso or the upcoming stm32 value line discovery), for less than $30 (about $7 for stm32 discovery), plus free ide / compiler (with some limitations).
with more money, you can go with keil - the best development suite I have used so far. and they support lots of platforms as well.
I would try to avoid the 8-bit chips. if you have to go with one of them, pick the avr, or even the stm8s as they offer considerably more than the pics at the same price, and offer upward mobility (the peripherals on the stm8 are compatible with those on the bigger stm32 chips).