We have missed http://forum.6502.org/viewtopic.php?f=2&t=2239. It contains the very curious results. Much cheaper 6502 outperforms 6800. It is more curious to compare 6502 with 6809... Of course, 6809 should be faster but is it only slightly faster or much faster?
Thanks to datajerk!
His results also shows than the Machin's formula algorithm is more than 2 times faster than the spigot.
BTW my results indicate that 65816 in 16-bit mode maybe only up to 50% faster than 6502 in the most cases.

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Pi-pack 18 is just released - http://litwr2.atspace.eu/pi/pi-spigot-benchmark.html. It contains the newer faster versions for 6502 based machines and a version for 6809 based Dragon-32/64. So it is possible to compare 6809 and 6502 at their edges. The results show that 6809 at 1.78 MHz matches 6502 at 2 MHz. The second accumulator gives a big advantage to 6809. However (IMHO) 6809 was overestimated. A lot of its instructions look clumsy. Its 16-bit index registers are slow with 8-bit ALU, so 6502 is faster with the tables. For example, pi-spigot requires 16-bit multiplication by constant 10000 with 32-bit result. 6809 with hardware 8-bit multiplication is slower than 6502 with 768 bytes table for this task. It was shocking that 6809 instruction to move one register to another requires 6 (!) ticks. 6809 uses Big-endian byte order and it makes it slower for addition or subtraction. 6809 requires more cycles to work with memory than 6502...
6309 which has 4 accumulators, hardware division and faster instruction execution timing should be the fastest for 8-bit architecture.

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Interesting findings. It does seem clear to me that little-endian makes most sense, but one still sees the opposite opinion now and again.

We probably shouldn't be too surprised that a table approach beats the hardware multiplier, but it's a bit of a shame that the multiplier isn't faster.