I am thinking of playing SoU again for the 20th time (it has been some time though) and I am thinking of playing a ranger. Is there much for a ranger in SoU and HOTU? Mainly I am looking for being able to talk to animals and get different dialog along with exclusive dialog and ways of doing things.
Animal Empathy can be useful, but remember that, the larger your party the less XP you get. Generally that's bad.
As far as the Ranger goes in this module, choosing a favoured enemy is difficult, if simply due to the large variety of creatures you will face. You'll face shadows, gnolls, kobolds, stingers, slaad and formians. Assuming you will wish to continue your character after SoU, I would suggest at least Outsider and Undead as two of your choices, since these creatures feature heavily in HoTU, along with Aberations. As far as the rangers race is concerned, I nearly always go Elf, since search is a class skill, and Elves always have search running. However, it is worth taking exotic weapon proficiency in order to use a handy Katana of the North (+1 attack, +d4 critical damage, +1 animal empathy, and best of all, endure elements x2 per day). I would also suggest taking a level of Shadow Dancer, and levels in either rogue or assassin, to pick up a few ranks in open lock, disable device and use magical device. Extra damage from surprise, and instant invisibility on tap, really enhances the ranger. Given that you will want lots of skills, you may want to have a decent IQ. A 13 intelligence allows for expertise, and given that you will need dodge and mobility for Shadow Dancer anyway, you may want to consider Weapon Master (with shortsword or a two bladed sword/scimitar) instead of rogue/assassin.
If I remember correctly, an animal empathy check was made in chapter one for befriending bears. Also, rangers were of a class that could better detect certain footprints. In later chapters, the ranger seems all but forgotten, with the branch of giving being the only token of consideration.
For HotU information you will need to post this topic there.
There's also a convo in Hilltop with one of the merchant's pets to discover a hidden cache.
But essentially empathy is used as a dominate creature spell without any restrictions on the attempts. Adding another party member to the ranger's (or druid's) entourage without depleting spell slots can be worthwhile. The dominated creature can be buffed and commanded just like any other summon.
I recall one AE-skill-focused exhange in HotU (a rat in the lower ruins of the maker's dungeon) that makes a non-critical subquest a bit easier. Other than that solitary occasion, don't think anymore were incorporated. But then, never made an effort to dominate any other creatures since most do not fall into the category of "animals" in that campaign. Some others may be immune to m-a effects, as well.
Still, it's fun to try it out and no real expense involved beyond the brief cool-down period. I've always wanted to enlist a Phase Spider in my party but forgot to attempt it. 
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AE was only really useful in part 1 of SoU, but a successful check in part 2 of HoTU on the rat (as stated above), did yield 250 XP's initially, and 500 XP later, certainly better tan taking on two lethal mithril golems that yield fewer XP's. Also in part 1, only with a ranger and either a druid or barbarian (can't remember which) did I have a chance of completing the White Stag quest.
