Ranger Identity Crisis
Conceptually, the Ranger suffers a great deal because it’s not particularly clear what it’s supposed to be – and the authors seemed as confused as anyone else. The original Ranger, perhaps, back when originally introduced to D&D, may have referenced Aragorn, but D&D-ified. I don’t know the history. But it was this original version that R. L. Salvatore used to create Drizzt do'Urden in his Dungeons & Dragons novels. These novels, more than anything else, seemed to inform Wizards of the Coast with respect to their 3rd Edition update.
Thus, the 3rd Edition Ranger is almost circularly-defined: it seems most based on modeling Drizzt do'Urden, a character based on the Ranger of an earlier edition. The problem with this is that Drizzt was a bit of a Mary Sue character who could do everything, and Salvatore took liberties with the class for the sake of the character. A novel’s author can do that, but a character class, not so much. A character can’t do everything, or at least if it does, it can’t do them all very well. So what you get is the Ranger, a class with a great hodgepodge of heavily-weakened abilities taken from other classes.
It’s supposed to be a warrior, so good BAB, HD, and some bonus feats, and it’s supposed to be a outdoorsmen, so good skills. It’s supposed to be related to nature, so it gets some Druid features – but because of the previous benefits, those features are drastically reduced in power.
As a result, you get a character who receives an Animal Companion that’s often too weak to do much more than scout. He has spells, which start late, have a very low Caster Level, and he only gets a very few of them. He has bonus feats for combat styles that focus on large numbers of attacks: those styles require bonus damage to work well. But the Ranger doesn’t get bonus damage. He’s supposed to know his enemy better than anyone, but Favored Enemy’s bonuses are tiny and wind up getting forgotten pretty often.
So the Ranger ends up with a bunch of half-features, and it’s very difficult to know where to take one and what to do with it.
Scout: The Specialist
Ultimately, the Scout isn’t really that much better than the Ranger, but at least the Scout knows what it is: it’s specifically based on an actual classical or medieval military role. The Greeks, the Romans, and medieval Europeans all had skirmishers in their armies that worked at least somewhat like the Scout. They’d move ahead of the main army, using hit-and-run tactics, and they were also excellent at reconnaissance, particularly in woodlands. This focus allows the Scout to do what it’s supposed to do, and do it well, and this specialization turns it into a better-designed class.
The Ranger does keep up because spells are powerful and because many supplements add new combat styles, alternate class features, and additional Ranger spells, while few add new features to the Scout. But a Core Ranger, or Core + Complete Adventurer Ranger, vs. a Scout? The Scout looks better to me. The Scout knows his role and simply does that well. It’s not a very powerful class by any means, but it is definitely better designed.
As @Lord_Gareth mentioned, the best answer for these two classes is to use Swift Hunter from Complete Scoundrel to get the best of both: Ranger adds better BAB, and grants you bonus feats that a Scout would want anyway. The Scout adds that bonus damage that the Ranger was badly lacking. The Ranger’s spells help shore up the fact that the Scout’s specialty, for all it does make it a better-designed class in a lot of ways, also leaves it vulnerable to having situations where it can’t really use its class features well. Spells are more flexible, which is exactly what the Scout needs.