The math difference between 3.5 and 2nd ed is an illusion. I do just as much math in 3.5 as I did in 2nd, it's just laid out differently in that regard. There are much more math heavy games out there that were as popular as AD&D was and I still meet people who have tried 3.5 and even 4 and prefer 2nd ed because in some ways, it's simpler to create a character and play.<br/><br/>The big difference between 2nd and 3.5 magic systems is the number of spells that you get. True, the progression (one 1st level spell at 1st, two 2nd level spells and a2nd level at 3rd, etc) and the spells are more or less the same, but in AD&D, you didn't get bonus spells for INT, WIS or CHA. You didn't just automatically know any spell you wanted and what you did get for higher int was a chance to have higher level spells later in the game.<br/><br/>As an example. at 1st level, a wizard or claric got 1 spell a day. That was it. You blew your wad in one bang and for the rest of the day you were pretty much trying to not get run through by a colbald. For high int, 18, for example, you had a higher chance to learn a spell and could, in time, learn the max level spells, if you could roll the percentile dice and make the roll.<br/><br/>In D&D 3.5 (as far as I know) and Pathfinder, you start off at 1st level with 1 spell, true, but you don't have to "learn" the spell to use it, and for high INT, you get bonus spells a day and all you really need to get the highest level spells, eventually, is a stat of 16. Again, no chance of not learning a spell the first time you see it, you automatically know it as you have no chance of failure to understand the spell. So, you could get up to 4 spells a day thanks to a ability bonus, which is a significant improvement over 2nd ed.<br/><br/>To further differencate between the two magic speaking. Both clerics and wizards were restricted bythe types of weapons and armor that they could use. If you wanted to be in the front lines, you had limited choices on how to do it and remain alive. I don't know if the hit dice are different for mages between the two versions. AD&D gave a mage 1D4 HP with a max con bonus of 2, so 6 HP, sucky armor options and basically, a knife or a staff as weapons. If you dual or multi-classed, you could use more weapons, but your armor was still restrictive. If you wanted a fighter/mage to stand up to the enemy, you either had to use one of your precious spells for defense, or take your chances and knowing that anything on the battlefield could cut you in half without much trouble.<br/><br/>In 3.5, the range of weapons is much broader, and you get feats to add to that, either inmagic or combat and if you're willing to pay for it, have a fairly decent armor selection that gives a relatively minor spell failure chance.2nd didn't give you that. Spells just did not work in most armors.<br/><br/>So, at a basic look, no there's not much difference between the two. Once you play 'em and get into the mechanics, the 3.5 wizard is much beefer than in AD&D.