hotShot, on 2010-October-30, 10:10, said:
8+1/3 means that we will have an 8 card fit most of the time, sometimes a 9 card fit and rarely only combined 7 cards in that suit.
When I hold 5 card in a suit, partners long time average is holding 2+2/3 cards in that suit, so I expect a combined 7+2/3 fit.
7+2/3 means that we will have 8 cards a little more than half of the time.
In SAYC and 2/1 opening 1♣and rebidding 2♣ over partners 1M bid, almost always promises a 6 card suit.
Bidding this way will lead us to a highly likely 8 card fit, but conceals the ♦ length.
Starting the bidding with 1♦ and rebidding 2♣ ( or 3♣ ) conceals the ♣ fit and it's hard to see how revealing this 9 cards can be an advantage, if it forces us to play an 8 or 7 card fit at the 3 level, or a 5-1 ♠ fit on the 2 level.
I would think that a more apt comparison is the frequency with which the auction
1♣ - 1♠
2♣
finds an X+ card fit in clubs
Compared with the frequency that
the auction
1♦ - 1♠
2♣
finds an X+ card fit in either Clubs or Diamonds