The Warm Up>>>Back to the Future
By far. I've never been a huge 9th Wonder fan - he's got so much uninspired, lazy production, he rarely switches his drums up, etc. But there's no denying that he's made many killer beats. Overall on this mixtape his work is lackluster, like b-side quality at best.
The actual songs aren't much better for the most part. It's alright, but pretty damn disappointing.
I wonder what his album will sound like. Most artists in different genres will put out an EP or something before an album. Rap artists spend so much time unleashing tons of mixtape material that they are often burnt out by the time it comes to make an album. IE you release some popular, critically acclaimed mixtapes, get recognition, then get a record deal, get your advance money, and slowly begin losing the passion/drive.