I've been both routes.... so I can say from experience I guess.... here's what I have to offer on the subject
Mail order: CJ @ JMS did an outstanding job with my chip. The car was still very much rich but close (right around 10:1 a/f) which isn't bad at all and very safe/conservative
Dyno: Got the can dyno'd @ True Blue Performance and got the a/f consistent throughout the power band right around 11.3/4 .... we also worked out some idle issues.
Obviously dyno tuning is much better because you can tweak as you go without waiting on mailing stuff back and forth which can take up to a month (a few days to send the chip and about 3 weeks or more to get it back).
Mail order is around $300
Dyno tuning is anywhere from $75+/hour (approximate #'s)
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