I know you wanted an answer from the airlines' perspectives, but unfortunately they don't post here so I will have to give you my perspective.

It really doesn't matter how many airlines are part of an alliance. I choose the alliance that offers the best product, at the best price, whose airlines serve the destinations where I wish to travel. For example I planned a RTW trip back in May for 2010. *A RTW product would work, but I would have to reduce the mileage of my RTW trip and it would have cost about $15,900 (including taxes) for a 39000 mile First Class ticket. I went with a OW 3 continent RTW ticket ex-ICN for $6600. The only problem was, that the main destination for which I was planning the trip was for a Live Aboard in the Maldives, and OW doesn't fly there, so I included a stopover in SIN and did a business class r/t ticket on SIN using UA miles. I could have purchased a r/t SIN-MLE business class ticket on SQ for about $1800 and still come out way ahead of the *A price.

Now since June 1 price increase of OW RTW prices and with CO coming on board with *A, if and when I plan a trip that includes Micronesia and Africa then I will probably book it on *A (CirPac referenced later). When I return to Australia and South America then I will probably go with OW. Now that is if the prices are competitive, otherwise I will mix and match like I did with the upcoming 2010 RTW trip.

Even with OW recent RTW price increases, they still come out way ahead of *A in terms of RTW ticket prices IMO. However, because of the substantial increase in OW Circle Pacific prices back on July 1 2008, I believe *A has better Circle Pacific prices the last time I checked which was the latter part of last year.

How many airlines an alliance has only matters if the airline is worth flying, has decent first class for the long haul flights (CX, EK, GF, QR and SQ come to mind) and decent business class for the shorter flights. So if an alliance has 50 airlines, the only ones that matter are the ones I need to fly for my travels (examples: CO to Micronesia or QF around Australia).

Oh and FWIW, all 3 alliances are strong IMO. Each one has its strengths and weaknesses.