it's so easy to overclock an AVR device because of it's single clocking architecture.I've already explained that the '51 requires special design proceedures to overclock given it clocks at either 12 or 6 division xtal clocks
hogwash first overclocking is NOT a parameter. Second the ability to handle a given clock speed has ansolutely nothing to do with divided clock or non-divided clock.

so 30MHz equates to 5 mips, crystals above 30MHz are usually 3rd harmonic which don't oscillate nicely, so a drop in crystal above 30MHz is hard to come by, this is not the case with the AVR.
many newer '51' s have PLLs

Sililabs produce nice chips but they are both expensive and difficult to prototype owing to their smd only package.
High speed and DIL gives some really nice reflections

The other point I wish to stress, is that output port pins on the '51 are normally common source with pull ups on their respective , they reach their limits very sharpish at 5 mips, i.e., looking at the waveforms communicating with a serial 13 bit a/d dont look good, much healthier waveforms can be seen from the AVR, doing the same job, which use the standard DDR in/out format.
hogwash a)many (even <$1) derivatives (e.g. the LPCs) of the '51 have configurable ports b) the quasi-bidirectionals have the "short hard pullup" which gives you very nice Waveforms unless you insist on crappy layout.

I have no problem with you using AVRs but do not accept that you promote them with false and/or unreliable statements.

Erik