Absolutely agree. Lennon and Harrison linked up with Moon and Entwistle might have been a tad interesting - but yes, neither amalgamations would have been a patch on The Beatles or The Who though.
There's no right answer here. Each case is different. I would rather go and see Townshend and Daltrey playing as Townshend and Daltrey rather than as The Who. Paul and Ringo would definately not be The Beatles (the Bootleg Beatles are much better anyway - they play stuff live that The Beatles...