I personally use a PIC, but not for the reasons already cited above.
Where I live, I have access to one electronics store, or after a 45 minute drive, I can get to two others.
So my choice is realyy based around what I can get, not the price.
Incidentally, the 4MHZ PIC16F84A is the same price as one of the ATMEL chips at my local store.
The difference being the PIC is a small 18 pin DIP, the ATMEL is a 40? pin chip.
The PIC wins for that reason.
Plus, coupled with the problem that I just built a PIC programmer, and nothing for the ATMEL, that pretty well also pushes me in the PIC direction.
PS I did make the trip to the city, and have two 20Mhz 16F84A's to play with, but alas no crystal