Warmage: Just a bad class
The warmage spell list is pretty awful, and Warmage Edge just doesn’t add enough damage to be worth it.1 Armored spellcasting is much too easy to do to get excited by it as a class feature.
Finally, note that warmage class features frequently don’t help wizard spells:
Armored Mage (Ex): [...] Nor does
this ability apply to spells gained from a different spellcasting
Warmage Edge (Ex): [...] The bonus from the
warmage edge special ability applies only to spells that he
casts as a warmage, not to those he might have by virtue of
levels in another class.
Neither of them is worth much in general, but they’re worth much less to you.
Long and short: adding wizard to a warmage certainly helps the warmage, but it doesn’t help the wizard much.
1 In fact, Warmage Edge isn’t even worth investing in Intelligence for a single-classed warmage above, say, level 5; the damage just isn’t enough to justify diverting resources from Charisma, Constitution, and Dexterity. At very low levels, it can be a kind of significant amount of damage, possibly justifying some investment.
Sorcerer: Far more powerful, broken with dragonwrought shenanigans
Sorcerer gets a far better spell list than the warmage, and with Greater Draconic Rite of Passage, you can make up one of your missed levels. With Loredrake (which you arguably might qualify for but a DM would have to be insane to let you), you can make up a lot more.
Ultimately, I recommend sorcerer, but not the shenanigans. They aren’t necessary and just break the game.
Beguiler: Not mentioned, worth considering
The enchantment/illusion version of the warmage, but without a lot of the problems. Like the warmage, the beguiler comes with a more-or-less static list of spells, but knows all of them. Unlike the warmage, that list is quite good, and moreover beguiler spellcasting is based on Intelligence, which works quite nicely for a wizard. Finally, it’s a 6+Int skill class, so it makes a great choice for ECL 1 when you get ×4. Just throwing it out there. Ultimately, you can probably do more with the sorcerer because the sor/wiz list is so great, plus there’s always dragonwrought shenanigans uniquely available for sorcerer, but beguiler is in many ways easier (less diving for spells) and more elegant (all Int-based).