As I recall, R&C and the first version of the wizard preview had the wizard's implement affecting things based mostly on their area types.
The revised wizard preview had removed the Tome implement, and changed things so the implements and traditions were tied to energy types instead. There is still a weak echo of this in the rules, with feats like Burning Blizzard (+1 damage with cold and acid spells).
I remember when 4e was first announced, and I wrote a rather lengthy post about what I hoped they'd do with damage spells to provide a more distinct feel to each energy type (not here, but on CM or NTL). I really didn't like the way they were pretty much treated as interchangable in 3e supplements - seriously,
scintillating sphere (
fireball but with electric damage) was an absolutely worthless idea, as was Energy Adaption.
The 3e PHB had the right idea, where energy types were considered pretty distinct. For example, I don't think the PHB has any acid spells that do a lot of instant damage, they're all "damage over time" spells. Similarly, sonic spells do low damage, but is better at destroying objects and very few monsters have sonic resistance.
I think my ideas were something like:
- Acid: low direct damage but can do a lot of ongoing, ignores SR due to being actual stuff instead of just energy.
- Fire: does the most direct damage, may have a bit of ongoing damage but not as much as acid. Little to no special effects. Big on explosions.
- Cold: Comes with side effects that slow and immobilize. Sometimes does partial physical damage (e.g. ice storm).
- Electricity: Side effects that stun. Tends to be either single-target or lines, not areas.
- Sonic: Low damage, hard to avoid. Extra-good against objects and object-like creatures (e.g. constructs).