Because it's easier to read when you're far.... or simply asked in some instrumentation equipment?
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With the USB PIC you can handle everything in ONE chip WITHOUT the need for any extra hardware in many case (ok some resistors and maybe some transistors). Yes it's a bit tedious the first time, but once you know how, it's not as this hard.

ANY PIC will also be WAY faster than ANY BasicStamp... and how about their prices ?

Be confident, get your hand dirty playing with them... they won't bite you