Here's a diagram explaining the differences between a 2 stock and 3 stock match's.
Time in minuets <---:---2---:---4---:---6---:---8---:---10---:---12---:---14---:--->
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Pools:
- 3 stock. (3 total)
- 8 minuets. (8 total)
- Best of 1/1.
(Estimated playtime average: 4 min.)
OR
- 2 stock. (4-6 total)
- 5-6 minuets. (10-18 total)
- Best of 2/3.
(Estimated playtime average: 6 min.)
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Main Tournament:
- 3 stock. (6-9 total)
- 8 minuets. (16-24 total)
- Best of 2/3.
(Estimated playtime average: 8 min.)
OR
- 2 stock. (6-10 total)
- 5-6 minuets. (15-35 total)
- Best of 3/5.
(Estimated playtime average: 8 min.)
(both arguably take up the same amount of time, but 2 stock best of 3/5 may take slightly longer.)
_________________
Tournament Finals:
- 2 stock. (8-14 total)
- 5-6 minuets. (20-42 total)
- Best of 4/7.
(Estimated playtime average: 11 min.)
OR
- 3 stock. (9-15 total)
- 8 minuets. (24-40 total)
- Best of 3/5.
(Estimated playtime average: 12 min.)
(Note: this does not take in to account time before, after, and in between matches.)
According to this diagram 3 stock best of 2/3 and 2 stock best of 3/5 arguably take up the same amount of time and stock. 3 stock best of 2/3 may be slightly more accurate and less time consuming, but it really doesn't matter what you choose because they essentially use about the same amount of time and stock.
However if you prefer slightly shorter, but less accurate matches 2 stock best of 2/3 is probably best for you.
If you prefer longer, more accurate, matches 2 stock best of 4/7 or 3 stock best of 3/5 would be better for you.
REMEMBER: The main legitimate argument is about time and accuracy.
<--------2----------[STOCK]----------3-------->
<-----LESS--------[TIME]--------MORE----->
<-----LESS---[ACCURACY]---MORE----->
<---1---2---3---4---5---> Stock #
<---1---::---3---::---5---> Best of #
It's easy to understand why 5 stock best of 5/9 may take up too much time and why 1 stock best of 1/1 may not be accurate enough. The issue is trying to establish a cut-off line in the gray area.