The relative utility of the various energy resistances

[Jowgen]

Unlike SR, DR and fast healing, it is relatively simple to stack up on non-trivial amounts of energy resistance as long as you get some spare gold or other character building resources, and also unlike those others, choosing what type(s) to resist is a rather involved choice.

Chief consideration is of course combat utility. If you expect to face dangers that employ a specific energy type, then the choice is easy. That being equal, the more common the energy type the better. AFAIK Fire is the most prevalent, followed by cold, then acid, and electricity at the end (with a sprinkle of sonic), but I might be off base there. Then again, if you're facing more optimized threats, you usually need straight up immunity, and even they might have access to immunity bypassers like searing fire.

Another consideration are added benefits of having a particular energy resistance. Fire and Cold respectively deal with temperature extremes, but that protection is pretty easy to get. More significantly, Fire has its own plane you mind end up on, where surviving without significant resistance to it is kinda tricky. Acid has the boon that it's a common environmental hazard a la Acid Pit. Electricity in contrast has no extra benefit at all to my knowledge.

There is probably a bunch of factors I'm missing.

So my general question is what kind of energy resistance do you usually prefer and why?

[Khedrac]

This actually depends on the type of energy resistance I am getting. (and I don't mean energy type).

Consider, the most common from of energy damage is fire, but fire resistance is also the most common form of resistance.
So, if a character is picking up a permanent resist X 10 they might want to go for fire as the most common damage type, but they may also want to not go for fire because fire resist 10 is of little use against attack spels so they will need a bigger resist for fire.

Example: I played a favored soul (well Barbarian 2/FS up to about 10 I think) - so for the FS granted energy resistance 10 I took Acid - which meant I got to ignore an acid arrow trap (and stand in the way allowing the rest of the party past safely). Acid attacks are unusual, but so is acid resist so it was useful to have that little bit of resistance.

Alternatively if the character is getting a big energy resistance, e.g. 50, then fire becomes a better choice as it means they can ignore most fireball and orb of fire spells the encounter without further buffing.

Now, one can substitute electricity or cold for acid in the first scenario fairly safely (though cold is probably the second most common resistance type and electricity the second most common damage type), but you should be able to see how the nature of the granted resistance will affect the choice of element.

I am not sure how a limited use resistance would alter my choice (e.g. 30 points/day or 10 rounds/day), but I think it would be like the small amount example, only more so. That said, having enough resitance to ignore the first fireball of a day (e.g. 50pts/day) would probably make fire or electricity a better choice.

If it is on the table go for sonic - it is a very hard resitance to get and the spell sgenerally do less damage as well!

[Venger]

I would slightly tweak your order, switching the places of electricity and acid as far as how common they are goes.

Monsters/npcs/etc will more commonly be able to cast lightning bolt or similar effects (say as slas) than any acid-based equivalent, so I'd rather have it than acid resistance.

I'd also go fire first unless I was building an uttercold assault necromancer and wanted to be able to carpet bomb myself for whatever reason. in that case, I'd probably get cold first, then fire, then electric, then acid.

honestly, I wouldn't worry about sonic. it's so rare, you aren't going to miss resistance to it often.

[Mike Miller]

I can't help but think the most important factor for energy resistance is the context of the campaign. For example, if it is taken place in the frozen wastelands and heavily relying on Frostburn material, you want cold resistance.

[Kurald Galain]

Don't forget negative energy resistance (e.g. deathless armor). That should help against a number of undead and evil clerics.

I'd go for fire and negative, carry a few scrolls or potions of Resist Energy, and leave it at that - unless you have a specific reason like a frost campaign, or immunity from specific own-or-allied attacks.

[Vaern]

I can't help but think the most important factor for energy resistance is the context of the campaign. For example, if it is taken place in the frozen wastelands and heavily relying on Frostburn material, you want cold resistance.
This. Not only will a campaign's setting affect what kind of creatures you're likely to encounter and what type of damage they're likely to throw at you, but if you can get a bit of fire or cold resistance then they effectively function as a substitute for Endure Elements in a desert or arctic environment, respectively.