Is an A H1N1 09 shot better than a mist?

They both provide the same immunity from H1N1 when properly given.

However, there are some indications for certain groups to use one over the other, but infants under 6 months old can not use either type of vaccine. The mist is approved in the US only for use in healthy individuals age 2 - 49. It is made from live attenuated influenza virus (LAIV), which means they have seriously weakened the virus strain with chemicals (or other processes) so that it can not cause you to actually get the flu. The inert ("dead") virus vaccines given in the injections don't give the same immune response unless injected. The live virus vaccines can be given by mist since the stronger, but still weakened, virus is able to produce the proper response without needing the more invasive injections.

 

UPDATE August 2011: New Intradermal Fluzone

There is also a new form of flu vaccine that is given with a microinjection system between the layers of the skin using an ultra thin needle. It is approved for those aged 18 - 64 and will be available in the US in the 2011-2012 flu season as well as in 40 other countries including Australia, Canada and some of the European nations.

 

More about the nasal mists:

Pregnant women should not take the nasal mist vaccines. Others for whom the mist is contraindicated include:


Although these groups cannot use the nasal mist vaccines, they are at higher risk of complications, hospitalization, and even death from the A-H1N1/09 flu, so they should get vaccinated but using the flu shot instead.

If you are moderately or severely ill, you might be advised to wait until you recover before getting the vaccine. If you have a mild cold or other illness, there is usually no need to wait.
Tell your doctor if you ever had a life-threatening allergic reaction after a dose of seasonal
flu vaccine, or Guillain-Barré syndrome (a severe paralytic illness also called GBS). However, GBS has not been linked to use of the live attenuated vaccines.

Mist vaccines can not be administered until 48 hours after antiviral drugs (such as Tamiflu) are stopped and antiviral drugs should not be administered until 2 weeks after the Intranasal administration (unless medically necessary by order of a physician).

The most common side effects of intranasal mists include runny nose or nasal congestion for all ages, sore throats in adults, and fever in children 2 to 6 years old.

Children 2 through 9 years of age should get two doses of nasal mist vaccine, about a month apart. Older children and adults need only one dose.

The nasal vaccine contains no preservatives.

 

More about the flu injections:

Pregnant women can (and should) take the injections.

The injections approved for use in the US do not contain adjuvants (compounds that potentiate the action of the vaccine to make less go farther in the production process). But they do contain preservatives unless you must avoid the thimerosal and then there are some single dose vials or syringes available by some of the manufacturers. However, the preservative use has been approved by the FDA and vaccines containing them have been safely used for the vast majority of recipients in the seasonal flu shots for decades. (The amount of mercury in that compound is less than a meal of fish contains.)

The injected vaccines are approved for use in individuals 6 months old and over. Adults need only a single dose and within 8 to 10 days, immunity is achieved. Children from 6 months through 9 years old must have two doses to achieve full immunity. CDC recommends that the two doses of 2009 H1N1 monovalent vaccine be separated by 4 weeks and full immunity should be obtained by 10 days to two weeks following the second dose.

Tell your physician if you have ever had an allergic reaction to a flu shot in the past or if Guillain-Barré syndrome has occurred within 6 weeks of receipt of prior influenza vaccine. Problems like these are extremely rare but should be reported prior to the injections. Also report if you have an allergy to eggs, chicken protein, latex, or any antibiotics.

Immunocompromised persons may have a reduced immune response to Influenza A (H1N1) 2009 Monovalent Vaccine.

The most frequently reported adverse reactions are mild hypersensitivity reactions (such as rash), local reactions at the injection site (tenderness, redness, swelling, pain), and the most common systemic adverse reactions were headache, malaise, and muscle aches.

See the related questions and links below for more information.