Magblade is the stronger choice. They fight at range, have access to damage shields, crap-tons of automatic self-healing, huge amounts of damage, endless sustain, crazy ulti regen.. best class in the game imo.

Stamblade can do a little more DPS, but the trade-off is: Dies easily, must play in mele range, no automatic self-healing, sustain is more difficult. Now, if you just like playing a mele character, stamblade is one of the best choices you can make.. outclassed only by stamDK.

Any magicka-focused race will work for magblade.. Dark Elf, High Elf, and Breton are the most popular choices. Any stamina-focused race will work for stamblade.. Khajit, Wood Elf and Redguard are the most popular choices. Argonian (my favorite) works for both. Read through the race passives and see what appeals to you the most.