I see this particular thread as a helper to people who are undecided. Maybe this should become a sticky thread. No one in CIS is asking why we are becoming citizen, and while there are 100 websites extolling the benefits of becoming a citizen, personal experiences (unlike someone just saying "2B american" repeatedly) can help others clarify their thoughts and nudge them one way or the other.
The most practical benefit is that as a citizen, the right to permanent residence is really guaranteeed without or almost without risk. Many
people may think this is relevant but you can argue any reason is
irrelevant. For example, others may say as citizens they can vote while
others say they do not vote anyway and even if tehy vote, as one invidividal one vote does not make any difference.
If you travel overseas, you will need to go thru a lof trouble if you lose your wallter with your GC in it. But as a citizen, you can simply
walk into any American embassy/consu;late for help if you lose passport/GC.
If you think all such events have very small probablity, then you
will not think even one good reason why citizenship is needed. Of course
you can argue for sentimental reasons, but let's get real. sentimental reasons
are meaningless unless they are based on some tangible benefits.