Well with that point of view, you can also say that all classes are just figher / archer / caster ...
Maybe with potential merges between them.
But that is not quite true.
You see by the basic difference that Wizzard is using Intelligence, and Sorcerer is using Charisma ... you can see that Sorcerers will excel in
Social situations, but Wizzard will have easier rolls in
Knowledge situations.
Then, if im not misstaken, there are spells for Wizzard and Sorcerer respectively, that other one cannot use.
(actualy Wizzard can right now, since he is able to learn litteraly anything that he find on scroll ... but we dont know it that would be a feature in final game, or if that is simple bug)
But again, as far as i know, Wizzard have much more utility spells than Sorcerer, wich is more focused.
Then ... but once again, unless i remember it incorectly ... there is the fact that Wizzard is preparing his spells for each day (right now in EA any time), but Sorcerer have all spells ready all the time ... so while Wizzard can have completely different list of spells prepared on each fight, Sorcerer have to work with what he have.
And last, but certainly not least ...
There is Metamagic for Sorcerers, that allows them to spend another resource to altern casting spell even futher ...
At 3rd Level, you gain the ability to twist your Spells to suit your needs. You gain two of the following Metamagic Options of your choice. You gain another one at 10th and 17th level.
You can use only one Metamagic option on a spell when you cast it, unless otherwise noted.
Careful Spell
When you Cast a Spell that forces other creatures to make a saving throw, you can protect some of those creatures from the spell’s full force. To do so, you spend 1 sorcery point and choose a number of those creatures up to your Charisma modifier (minimum of one creature). A chosen creature automatically succeeds on its saving throw against the spell.
Distant Spell
When you Cast a Spell that has a range of 5 feet or greater, you can spend 1 sorcery point to double the range of the spell.
When you Cast a Spell that has a range of touch, you can spend 1 sorcery point to make the range of the spell 30 feet.
Empowered Spell
When you roll damage for a spell, you can spend 1 sorcery point to reroll a number of the damage dice up to your Charisma modifier (minimum of one). You must use the new rolls.
You can use Empowered Spell even if you have already used a different Metamagic option during the casting of the spell.
Extended Spell
When you Cast a Spell that has a Duration of 1 minute or longer, you can spend 1 sorcery point to double its Duration, to a maximum Duration of 24 hours.
Heightened Spell
When you Cast a Spell that forces a creature to make a saving throw to resist its Effects, you can spend 3 sorcery points to give one target of the spell disadvantage on its first saving throw made against the spell.
Quickened Spell
When you Cast a Spell that has a Casting Time of 1 action, you can spend 2 sorcery points to change the Casting Time to 1 Bonus Action for this casting.
Subtle Spell
When you Cast a Spell, you can spend 1 sorcery point to cast it without any somatic or verbal Components.
Twinned Spell
When you Cast a Spell that Targets only one creature and doesn’t have a range of self, you can spend a number of sorcery points equal to the spell’s level to target a second creature in range with the same spell (1 sorcery point if the spell is a cantrip).
To be eligible, a spell must be incapable of targeting more than one creature at the spell’s current level. For example, Magic Missile and Scorching Ray aren’t eligible, but Ray of Frost is.
(copied from:
https://roll20.net/compendium/dnd5e/Sorcerer#content )
