I think it would be more like an Impreza v F430. 95% there over most of the way, but it's the extra 5% that makes the Ferrari special and therefore lusted over.
In the interests of being boring though, you can actually quantify the differences between two PB10s against one PB13 by referring to the usual online resources.
Assuming that the two PB10s were co-located in order to achieve a near 6dB gain in performance, it's not too much of jump to simply compare the results of the two subs. Simply comparing the 90dB plot for the PB10, against the 95dB plot for the PB13 as the two PB10s would deliver approx 95dB performance with each one running at 90dB.
The results against the PB13 running a 20Hz tune:
Max output at 20Hz: 2xPB10=101dB, PB13=107dB. That means
four PB10s would be required to match the output.
Max output at 15Hz: 2xPB10=89dB, PB13=99dB.
Running the PB13 in 15Hz tune at no cost to the 20Hz figures lifts the 15Hz output to a staggering 103dB requiring
eight PB10s.
The PB10 has no other tunes and I'm ignoring 'sealed' as a tune as it's pointless.
THD @ 20Hz @ 100dB: 2xPB10=10%. PB13=5%. Four PB10s required to match.
THD @ 80Hz @ 100dB: 2xPB10=11%. PB13=2.5%. Eight for a match. Gulp.
The differences at 20Hz may not be so noticeable due to the human ears sensitivity at such frequencies, but it certainly will be at 80Hz.
So the advantages of multiple PB10s. Research by Harman Group published in a white paper showed that significant equalisation of room modes could be achieved across a wider area if a sub were positioned at the centre point of each wall assuming a regular room, requiring four PB10s anyway.
The down side(s)?
You would then only achieve a 3dB increase in performance for each doubling of the number of PB10s, so
eight PB10s co-located at the mid points would be required to match the raw performance of one PB13 where only four were required above and thus sixteen to match where eight were previously required.
You could keep adding PB10s until you go blue in the face, but the PB13 will go deeper, period. The PB10s could be equalised to deliver a similar depth, but to achieve a flat frequency response at 15Hz would require reducing the rest of the frequency to be down tuned by about 8dB. By now you'd be better off selling your house and living in PB10s to gain the performance back.
By the time you've bought four PB10s, you could buy two PB13s and that would require all of the above totals of PB10s to be doubled again. NOOOOooooo
ooooo! BTW, I'm taking into account the cable bill in that calculation.
Any corrections to my 'back of fag packet' calculations gratefully received, but there'd still be no point; Buy one PB13 or two if you're a mentalist with no neighbours.
Russell