http://machonshilo.org/en/eng/list-ask-the-rav/57-shophar-lulav-sukka/80-etrog-type What type of ethrog should I buy?
Answer
One should buy a Yemenite etrog.
Also Q and A from this Rav (Rav Elbaz)
Do you know if a number (2 or 3 for example) of people are able to all use 1 set (although not better still is it acceptable).
Or put another way- is it better to own less quality or questionable Etrog (and whole set obviously) individually or share a higher quality set with someone else?
Do you consider for example a Moroccan Etrog set or another variety using it as making a Beracha Levatalah, or just better to have Yeminite species only as hiddur Misswah?
Also let's say in a situation where their would not be any Teimani Etrogim available should people use other set's and with a Beracha?
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Although Yemenite Etrogim are most certainly the most halachically preferred species of etrog, many Poskim consider moroccan Etrogim Meyuchas as well and kosher for the blessing. I would not go so far to say that making a Beracha on any other kind of etrog is a Beracha levatala, however, like the poskim say, it is preferable to take an etrog which is CERTAINLY not grafted.
Although it is preferable for each individual to have his own set of lulav and etrog, there are definitely halachic ways to permit several persons to share one set. First of all, from the third day of Sukkot on (in israel from the second day on) a borrowed lulav and are perfectly kosher to make a blessing on. Even on the first two days (first day in israel), the owner may give his lulav and etrog to another (or several others) as a gift and tell the recipient "this is a gift to you on the condition that you return it to me." in this way, the recipient may recite a blessing on it with no problem. (for a synopsis of these laws, see Sukkah 41 and Shulchan Aruch chapter 658). This can surely be taken into consideration if one has money for only one etrog Meyuchas or several not such meyuchasim.
Shabbat shalom and Gmar hatima Tova,
Meir Gavriel Elbaz