Best is subjective...for example, the carnuba's are best if you go off road, as the finish is harder and most scratch resistant...whereas the shine that you can get from the silicones can be impressive and last a long time...and repel acid rain and guano, etc very well.

So - for an Altima that you drive on the street, and the impression I get that you are not going to enter it in a Concors de Excellance type of thing, I'd say a silicone that goes on easy so that you do it on a regular basis is best (2x/yr).