This is the common question asked when someone comes to me to do teeth whitening.
I would not answer the question in this manner. I would rather compare it based on the needs and compliance of the individual.
If you are getting married tomorrow,then obviously you will need to get an “instant” whitening ie the chair-side in-house whitening.On the other hand,if you are  generally a compliant and disciplined person who is willing to listen to your dentist’s instructions :),then go for the take-home overnight whitening.
The end result?  They both give you white teeth.

Below are some before and after pictures .

The 1st picture was  taken in June 2009 .The 2nd picture was taken 2 weeks later after using the take-home whitening which was applied on the upper teeth only. This lady of 68 years old, continued with the whitening procedure for her lower teeth for another 2 weeks.(This process can be done together ie the upper and lower teeth can be whitened at the same time).The 3rd picture was taken recently in September 2010. obviously the patient is very happy with the results.

The above are pictures of a chair-side whitening patient,obviously a very happy young lady of 19 years old.

In summary,you can will get results irregardless of the type of whitening you do.