The main problems with annexation are that if it is a different culture as in the Spanish sweeping North Africa, you will get very little from the territory, especially once revolt risk is factored in. A satelite will not have the same problems and will still send you money.
Though as has been pointed out, manpower is almost always more inmportant than money (except the Russians). You can force the satelite to give you any troops they raise as expeditionary forces but that is obviously not the same as rasing another French guard brigade from the points.
There are many tradeoffs. As Spain, I defintely prefer to satelite Algeria or Portugal simply because it takes two wars to annex all of them. Tunisia, on the other hand, is easily swalloed in one gulp. In Morroco the only part you care about is in the north and Tangier has good income, so again I'd annex there.
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