Consider the Orc it doth neither spin nor doth it sow.. Whoops - wrong allegory. Rather my work on the HCEG has made me interested in the nuts and bolts of how experience has been calculated across the editions. My thoughts from my earlier work are that I will find a wide disarity between XP values between 1e and 3e and that 3e will be arbitrary. So I'm doing a series analyzing the XP values for individual monsters starting with the common Orc - homo sus orca.
In the table below I've laid out the statistics by game system with the right hand column being the total 1e XP earned for the line. The 1e Experience Point system (DMG p84) uses the formula Basic XP Value + XP per hit point + Special Ability Bonus per Ability + Extraordinary Ability Bonus per Ability. These values are adjusted by the creature's total hit dice, these are summed up in the row Calculated 1e XP..
|Average Hit Points||4||4||4|
|Average Treasure||2d6 GP (7)||300GP/2|
|7 | 150|
|Calculated 1e XP||25||168|
The difference in the XP earned for slaying an Orc between 1e and 3e is dramatic to say the least. And because the creature hasn't changed, it really comes down to the treasure value. And it's not just that a 3e Orc is wearing better armor or that that is being taken into account on the treasure - scale mail is only 50gp in 3e, leaving over 2/3rds of the increase unaccounted for.
One of the other oddities that I noticed is the difference between the pre-calculated XP in 1e (from Appendix E) and what the formula derives. It appears that Appendix E does not give them credit for having missile weapons. The gap between the formula result and the pre-calculated results are consistent across the systems, in both cases the pre-calculated result is less than what the formula gives.For 1e its 85% of the formula, for 3e its 89% of the formula. Interesting but with only one data point not of any significance.
The impact of the disparity on game balance is huge, in 3e seven orcs is all it takes to raise any character from 1st to 2nd level. In 1e, using the formula, it takes sixty orcs to raise an assassin or cleric to 2nd level, 80 for a druid or fighter, 90 for a monk or a ranger, an even 100 for a magic user and a wearying 110 for a paladin,.
Probably not an original thought, but I think I just found the mathematical difference between Old School and d20.