My character is a High Elf and specializes in magic. Dual casting takes a lot of mana but I've noticed it wipes out a lot of the low level enemies. What is best? Dual casting, where the mana runs out quicker, or having a sword in the other hand?

This question goes for any hostile creature in Skyrim. My character is a Level 2 (started over). Wanted your opinions on this topic.

Thanks.

Well, it depends what sort of 'build' you want to play. If your character uses a melee weapon, he/she is more of a battlemage than a mage.
If you just want the stats, well ... melee weapons will be better than magic, because of smithing and such.

Depends if there are other enemies nearby that you may need the magicka for.

Level 2 might be a little low to try and dual cast with no enchantments at least.