Flames of War discussion alert! Don your asbestos lonh johns!!!
I now have both. I also have "Desert Rats"
I spent no money on NA, by the way. I got it in trade for painting, so
Anyway, here is my mini review.
NA is more restrictive in terms of what is permitted where. Take my Sikhs. In Afrika, they are Fearless Trained, and get all kinds of stuff. You are on your honor to make your list "historically", That did not prevent me from fielding PIATS, Blacker Bombards and Churchills in one past game. I was called on it, but gave the Orwellian reply "Whatever is not forbidden is cumolsory." Sue me. 
NA breaks things down by theatre: Africa, Tunisia and Italy/sicily. These "options" are not as free.
On the other hand, with the new format, a lowly company commander has access to a real treasure trove of goodies. A Motor Company has only one required Motor Company choice, and that is only 20% of his "army". Katy bar the door.
NA has gone over to the Dark Side of catering to the mathematically challenged. 'Nuff said about that. The restriction on number of Support choices are now gone. It is now the newer Chinese Menu choice. (One from each box in Column C)
The extensive (two or 3 pages) on the mysteries of tank markings are gone. Oddly enough, I found this best treated in "Desert Rats", slightly less so in Afrika.
The Fallschirmjaeger and Parachute and glider rules are also missing.
I find the Infantry Tank Company interesting. It is different, and gives me an excuse to buy more Valentines, possibly my favorite 8th Army tank.
I have not thoroughly read the American section yet, but it looks like they have not been upgraded to Veterans in Italy yet. I could be wrong. The Yanks do have the thinnest page selection.
My feelings on the book (North Africa) are that if I got a look at it before I bought it, I would probably not have bought it. Since it was essentiallly free, I am glad I have it, if only for the new restrictions, AND more options. This means essentially that I can play the list game with a ourer conscience.
Compoany commanders STILL get the freedom of choice that would make a regiment commander jealous.
In other words, if you do mostly historical gaming, your armies will be slightly more realistic and historically valid with NA. f you do primarioy tournament gaming, your choices are both more restrictive and looser. You haveto have a familiarity wth the game to know what I mean.
However, I think the parts missing from Afrika negate that.
Overall, I find Afrika a better guide. If you are going to charge 50 bucks for North Africa, why leave out so much good stuff from Afrika?