[Avodah] Is it better to have one person do a vadai mitzvah or a number do a safek mitzvah?

[Micha Berger]

Back in v176, on Fri, 24 Aug 2007 18:11:52 +0100, Rt Chana Luntz
<chana at kolsassoon.org.uk> wrote (long quote because of the post's
age):
:> It is pertinent to point out that in the mishna's case, each 
:> of the 5 brothers has with 100% certainty done a mitzva. This 
:> is because chalitza to one's yevama is a mitzvah min haTorah. 
:> Thus in the mishna's solution, each brother has with 80% 
:> probabilty  performed mitzvat yibum, and with 20% probability 
:> performed mitzvat yibum. In the alternate possibility, when 
:> one yavam marries all of the y'vamot after each of the other 
:> brothers have given chaliza to all of the y'vamot, each of 
:> the choltzim has with certainty done mitzvat chalitza, and 
:> the the fifth brother has with certainty done mitzvat yibum. 
:> Thus although the presumtion of the g'mara is that yibum is a 
:> greater mitzva than chalitza, in any event everyone will have 
:> done, with certainty, either yibum or chalitza.

: This is all true, but why does this not make matters worse, rather than
: better?  Given that everyone will have done a mitzvah, either chalitza
: or yibum, why not have one person who knows he has done the vadai
: mitzvah of yibum, and four who know they have done the vadai mitzvah of
: chalitza.  Instead, everybody will have done a safek mitzvah of yibum
: and a safek mitzvah of chalitza - ie two sfekos.  Now agreed that one of
: those sfekos has to come up trumps, ie if one has done yibum one has not
: done chalitza, but if one has not done yibum, one has indeed done
: chalitza, meaning everybody gets a mitzvah apiece, but it is equally
: true that everybody gets a mitzvah apiece if you go the other way - and
: at least that way, everybody knows which mitzvah he has performed.  

Doesn't this presume issues like the validity of sefeiq sefeiqah she'einah
mis-hapeches and whether one can combine two unrelated sefeiqos?

GCT!
-mi