As per the previous comments, in my experience, it's almost always both. A
good business plan certainly helps (and if it's really good enough it could
help considerably), but having a good background in business and a track
record of managing your money well is pretty key.

All loans are risk based and therefore if your credit or previous experience
(either in business or managing your own money) is non existent then it's a
higher risk. If your credit or experience are just bad, then based purely on
your previous record, the way you will treat any new funds is also a risk.
Getting a low down from Experian and Equifax is definitely a good start and
you may be able to identify things you could improve on - for instance,
paying a credit card on time, consistently and in full can improve your
record in no time.

Your personal credit will impact any lender’s decision on your loan
request. This is specially true of small business loans where the line
between the business entity and the owner/operator is many times blurred.

I underwrite million dollar deals for a living, and we still look at the
credit history of the guarantors. The fact is a bad credit history is not
that uncommon. Many people get credit blemishes as a result of divorce, long
periods of unemployment, health crisis, or other. However, it is important to
show that there has been an effort to pay back those debts.

Another aspect you have to take into account is that a lot of the small
business lending has been automated, and your request is likely to be
reviewed through a process called “credit scoring”, which uses a formula
that takes personal credit history into account.

Yes you will need a credit report from one of the top three credit reference
agencies either: Experian, Transunion or Equifax, best thing to do is check
out the business checklist, it will tell you what you need to do:
http://www.sba.gov/content/business-loan-checklist

SBA loans mostly requires that you've in business for at least 2 years or
more, be profitable, have increasing revenue trends, good credit, and
collateral.

A business plan is not required for an SBA loan unless you are applying
specific for a 7A startup (extremely difficult to obtain at any time).

Both. You need a well written, comprehensive business plan to get in the
door. You also need a good personal credit history to qualify for a loan.