What is your main goal for your FF miles? Benefits/status when you fly for work? Award redemption options/availability when you redeem for pleasure? Do you have any significant leisure travel, and if so to where and will you purchase or redeem miles for those tickets? Do you fly Coach or First for work domestically? Coach, business, or first for work internationally?
What did you read about DL that gave you second thoughts?
Sorry, lots of questions, but I think if some of this information is included in your query, you'll get better advice.