Don't know what a "b5" is, but if you mean Audi S4 for the second one, don't know how you can compare them. Maybe two GTIs, one for daily commutes, one for weekends, vs. an S4 would be a fairer comparison price-wise.
Oh heck, a used S4 would be great. Especially since the newest incarnation is so god damned ugly. Those model years are by far the best looking of the A4 line.
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